iPhone apps are extremely useful in our day to day lives, great design and user interfaces enhances our experience and makes us want to use it more, thus solving  day to day problems become whole lots of fun while enhancing productivity. Here are 21 essential iPhone apps that are extremely useful, coupled with visually appealing interfaces. If you have any recommendations please feel free to leave a comment. Enjoy!

Groups

[$2.99 | Website | iTunes]

A highly potential iPhone native “Contacts” app replacement. With groups you can manage your contacts easily, organizing them using drag and drop. Your created groups will synchronize with iPhone’s Contact app. Email groups of people easily with this app, call or SMS anyone easily, all with a very sexy interface.

User Interface

Cha-Ching

[$2.99 (Introductory Price) | Website | iTunes]

Cha-Ching was originally a Mac app (current version 2.0 beta, free until 30 April 09) designed for personal finance management. The highly anticipated iPhone app was only recently released at the App Store. I’ve tried many similar apps of the same genre and this is the best looking one in my opinion.

User Interface

Analytics

[$5.99 | Website | iTunes]

Analytics lets you check your Google Analytics data and reports on the go. At times you might find this app even easier to analyze Google Analytics data than the web app.
User Interface

Ego

[$1.99 | Website | iTunes]

Ego gives you one central location to check your Mint (number of visits), your total number of Twitter followers, Feedburner stats and Google Analytics stats on the go. Very convenient way to streamline the checking of your numbers, or your ego so to speak.
User Interface

Weightbot

[$1.99 | Website | iTunes]

Weightbot is a weight tracking app designed to let you meet your weight losing goal. Set your goal weight, record your weight at any interval (one weight per day max), view your BMI, and see your progress on a beautiful graph.
User Interface

Tweetie

[$2.99 | Website | iTunes]

Tweetie is (in most people’s opinion) the best Twitter iPhone app available on the App Store. The most distinctive difference between Tweetie and the rest of the Twitter apps in the store is it’s extremely smooth scrolling. You can do most major functions like reply, direct message, retweet, Twitpic, Instapaper integration, search, save searches, trends or even look at tweets by nearby tweeple (using the GPS) etc.
User Interface

Tumblr

[Free | Website | iTunes]

If you use Tumblr, you’ll love this app as you’ll be able to update your Tumblr blog easily.  Most often than not I use this app to quickly snap pictures and upload it to my Tumblr.
User Interface

Byline

[$4.99 | Website | iTunes]

Byline is an RSS reader that synchronizes flawlessly with Google Reader. The best and most good looking Google Reader app I’ve found, the plus point of this app is that for every article you marked as favorite, the whole article will be downloaded into Byline so that you can read it offline, good feature if you want to read your favourite articles without having to wait for the article to be downloaded while on your daily commute.
User Interface

Tags

[$2.99 | Website | iTunes]

Tags is a Delicious app that syncs all your bookmarks from your Delicious account. I guess the reason why this app is named “Tags” is because of the unique way your bookmark tags are displayed (as seen from the screenshot). If you’re a Delicious user and there is only one app you can download, make it this one.
User Interface

Satisfaction Remote

[$1.99 | Website | iTunes]

This is an accompanying app for Get Satisfaction users who wants to check discussions on the go. Find companies, products or people, find and read support topics of your favourite apps. Reply or comment on a topic.
User Interface

iStat

[$1.99 | Website | iTunes]

iStat lets you remotely monitor your Mac’s CPU, memory, disks, temperatures, fans, uptime and load averages all from your iPhone. This app also lets you see your iPhone’s stats for memory, disk space, WiFi and Cell IP addresses, uptime & load averages, plus view and email your iPhone’s Unique ID and MAC address. Pinging and traceroute functions are also supported.
User Interface

CompareMe

[$1.99 | Website | iTunes]

This app lets you compare any 2 product’s prices by their quantity, volume, lengths etc. A simple example will be – 3 for $1.75 or 2 for $1.35, which is cheaper? CompareMe will tell you that in a split second. Good for price conscious shoppers, helps me heaps when doing grocery shopping!
User Interface

Tipulator

[$0.99 | Website | iTunes]

Having trouble doing mental calculations on the tips you need to pay on top of the total price of your dinner and how much each of your friends need to pay? Tipulator solves this problem, with a literally “sweet” looking interface.
User Interface

Measures

[$1.99 | Website | iTunes]

Measures lets you convert units like currencies, temperatures, weight, distance etc. What I like about this app is not only the interface and the icon, there is an inline calculator built into the app for calculations while letting you view the converted value during the process. Great when shopping for multiple items at a foreign country.
User Inteface

GuitarToolkit

[$9.99 | Website | iTunes]

GuitarToolkit is packed with a slew of utilities to compliment your guitar playing experience. It includes the most notable guitar tuner (using the iPhone microphone) which proves to be extremely accurate, a metronome, a library of over 1500 chord variations which is highly recommended for beginners learning guitar.
User Inteface

Inquisitor

[Free | Website | iTunes]

The very popular Inquisitor browser plugin now comes to the iPhone. With the same sleek interface, Inquisitor lets you quickly search anything on the web. Keep in mind that the search engine used is a Yahoo search engine, if you’re a staunched Google user you might not be very fond of that. But if you’re a staunched designer, the sexy interface will make up for it.
User Inteface

Flickit

[Free | Website | iTunes]

At last, an iPhone app that lets you upload multiple photos to Flickr! Via a beautiful interface (and can’t believe it’s free!), you can snap a photo or choose your desired photo(s) from your photo library for upload.
User Interface

Night Stand

[$1.99 | Website | iTunes]

Night Stand displays a beautiful, vintage LCD clock on your iPhone or iPod Touch. It sports two variations: flip clock and vintage LCD display. There’s also an alarm clock built into this app.
User Interface

Faces

[$0.99 (Sale for a limited time) | Website | iTunes]

Faces is a visual quick dial application. Calling or SMSing a friend is just a click away upon launching the app, launch time is quite fast I would say. You can also sort contacts into groups so that you can find your desired person to call/SMS more easily. Yes you can find many quick dial apps on the store, but spotting one with a pleasing interface is hard. You can even customize the background by using a picture from your photo library.
User Interface

Classics

[$2.99 (Sale for a limited time) | Website| iTunes]

Classics has one of the best user interface for reading classic tales including Gulliver’s Travel, The Time Machine, Frankenstein, Alice’s Adventures in Wonderland (illustrated), The Wonderful Wizard of Oz, among many other books. Highly recommended for classic tales fans, even if you’re not you might just fall in love with it.
User Interface

Things

[$9.99 | Website | iTunes]

The very popular and extremely useful GTD (Getting Things Done) productivity app deserves a mention here. If you have not heard of Things, this app lets you handle your to-do lists systematically. Also check out the awesome Things Mac app.
User Interface

ConvertBot

[$0.99 | Website| iTunes]

For only 99 cents, you get an awe-inspiring unit converter that converts angles, area, currencies, length, mass, power, pressure, speed, temperature, time, volume etc. One thing to note is that only a couple of currencies are supported, do check if your country is supported at the App Store before buying.
User Interface

Outpost

[$12.99 | Website| iTunes]

I have always wanted to try Basecamp but haven’t found the reason to, but if you are one proud user, you’ll be able to appreciate this native iPhone app for Basecamp. Outpost brings the power of Basecamp to your iPhone or iPod Touch, with comprehensive support for messages, milestones, to-dos, and comments. Outpost is also the first app for Basecamp which offers full offline capabilities.
User Interface

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