Have you heard of the App Store? It's pretty important to the iPhone apparently, and has turned what might be a normally decent smartphone into a conduit of expandability.

Let's focus first on what's already on the phone, as it's already pretty impressive. As well as the usual suspects in the iPhone version of Google Maps, YouTube and Yahoo! weather, we're now joined by an upgraded calculator, a compass function and Voice Memos to boot.

The iphone 3g s

The compass is probably the most pivotal new application, as well as video recording as well, as it gives developers a couple of new tools for some interesting new Apps. We've already seen the likes of the Seer Applications for Android from IBM, which gives Wimbledon fans the chance to link the compass, GPS and video stream together to learn about aspects of the tournament just by holding the phone up to a certain landmark.

Google Maps now makes use of the compass, but it's a little bit confusing. Not only does the compass constantly need rebooting as it gets 'interference' from other devices, it's also erratic functionally. When trying to find your own location in Google Maps, you can find out which way you're facing, which is really helpful should you be lost.

The iphone 3g s

Finding your location was super speedy, much better than the likes of the HTC Touch Diamond2, with around 15 seconds the average time to locate. However some people may struggle to know how to use the compass properly, as you'd assume there would be some kind of 'compass on / off' toggle in the settings, when actually it's activated by a double, rather than a single, tap when finding 'My Location'.

We're excited to see how developers use this new bit of functionality, as the HTC Magic and G1 both use it to show off Streetview so well, so when the Apple crowd get their hands on it we can only imagine what might appear.

The iphone 3g s

The iTunes store has also been given something of a refresh as well, albeit minor, as you can now download audiobooks and movies to the device, as well as being able to enter redeem codes for iTunes vouchers from loved ones at Christmas. It might not seem like much, but it certainly adds to the holistic iPhone experience.

On the App Store side, we're not only being treated to micro-payments (ie being able to subscribe to your favourite magazine or newspaper and pay for certain parts or periods) but a general expansion of applications available. The panorama is set to expand as well, as more applications with greater functionality and add-ons come to fruition. For instance, we're very excited by turn by turn directions and a TomTom dock and speaker, and LifeScan, allowing diabetic users the chance to monitor their blood level, is just the next level of cool.

Here are a few applications currently available that we think every discerning iPhone owner should have:

TweetDeck - Great for bringing order to your Twitter account, it organises your friends for you, has separate columns to keep your information in check, and allows you to shake and refresh.

Google App - There is literally everything Google here and even more than on the Android OS bizarrely. We're talking Voice Search (scarily accurate) Google Earth, Mail and Talk, a YouTube portal that syncs with the iPhone's YouTube client and loads more. Worth getting for the cool factor of Voice Search alone.

Need for Speed Underground - a great showcase of the iPhone 3GS's abilities graphically, and the frame rate and in-depth game play, along with the sumptuous cut scene videos, will have you whipping this out on practically every bus ride.