Wakoopa, the software-tracking tool, will soon support iPhones. The service will work in a very similar manner to its Windows and Mac versions, as it will track the applications you're using on your iPhone. Wakoopa for your iPhone is set to be released tomorrow, and will be found here.
The data is saved to your Wakoopa account, where it can then be shared with other users and friends. This essentially helps create a useful version of Apple's application directory, as you can see how many people are using particular applications, as well as who these users are. Find trusted applications by seeing what you're friends are using on their iPhones as well.
A complete mobile site has been created to grant you access from your iPhone, so you can see the list of applications as well as their associated stats. Data on iPhone apps are also available online, and can be found here.