In order to check the amount of data sent and received over your mobile operator from the iPhone, select Settings.
Tap on General:

Each address book added to the iPhone, be it an Exchange account, Google account, or contacts stored on the iPhone itself, is assigned a "Group" in the Contacts application on the iPhone. Sometimes it is necessary to copy or move contacts between these groups, for example if you wish to backup contacts stored on the iPhone memory and are unable to sync with Outlook on the desktop. In this situation you could create a free GMail account, set it up as an account on the phone (selecting the option to synchronise contacts), then move or copy your contacts into this new group.

It has long been possible to create configuration profiles for the iPhone and iPad, store those settings in a single file and deliver that file to devices via email or by download from a web server, by using the iPhone Configuration Utility.
This functionality has been incorporated into the release of Mac OS X Lion Server, in the Profile Manager feature.

UPDATE - this article does not apply to the iPhone 4S: the option to disable 3G is not present.

Should you be in an area of only intermittent or poor 3G coverage, you may wish to set your phone to 2G only mode to experience a better service until you are next in a better coverage area.

To do this, launch the Settings and select General

Should you be experiencing poor signal strength or no service, it is occasionally necessary to perform a manual roam on your device to de-register it from your network provider and then re-register it again.

Siax is a fully functional VoIP client for the iPhone, providing support for both SIP and IAX protocols, enabling you to make intra-office calls remotely via either 3G or WiFi connections directly from your iPhone. Interfacing with your existing contacts list and providing support for multiple VoIP accounts, Siax is very intuitive to use and easy to configure. Note, however, that Siax is not free, licenses costing in the region of £6, and also requires that your iPhone be jailbroken.

Google has launched a new service, still in beta, enabling users to send print jobs from their iOS or Android powered device to a remote printer over the air.
The system currently only works on Windows, requires the latest beta version of the Google Chrome 9 web browser and obviously requires that your PC and printer be powered on.

AirPrint, included with the release of version 4.2 of the iOS software for the iPhone and iPad, is Apple's technology enabling wireless printing directly from your iOS device to an AirPrint-capable printer.

Apple's AirPlay technology, included with the release of iOS 4.2 for the iPhone and iPad, it is possible to stream music directly from your iOS device to a set of audio speakers (or an amplifier) connected to an Apple AirPort Express device. At the time of writing there are only a limited number of AirPlay-enabled speakers, but the AirPort module can be connected to any set of portable speakers or an amp via a standard 3.5mm connector.

VManage for iPhone is an application that enables remote management of a VMWare infrastructure, allowing administrators to power virtual machines on and off while out of the office, view status of machines and track any alerts.

For more information, view the application's entry in the iTunes Store Here