Question: I have seen similar posts but couldn't find any answer..

Kindly advise whether its possible or not?

Answer: 
Are you talking about 3rd party applications or the inbuilt applications of the iPhone?

If you are talking about 3rd party application then forget it.. As told by @KingOfBliss apple restricts it.

And if you want to open inbuilt applications like camera, photo, contacts,safari web then you can do it.

You can get sample code for implementing all these from [here](http://developer.apple.com/library/ios/navigation/#section=Resource%20Types&topic=Sample%20Code)...

Hope it helps...

hAPPY iCODING...
Applications can register a custom URL format, and then other applications can call that URL to trigger that application, pass it data, etc. Some of Apple's built-ins have URL formats that they've published, and some 3rd party apps have (and advertise) them too. If you're building more than one app, you can obviously customize your URL scheme to have your apps talk to each other more or less freely.