How can i detect other iphone apps is install or not?

I want detect the apps on iphone which is install or not…If i get the UDID apps also cant work properly…Do you all have another best solution to detect other apps are install or not?

As far as I know, the sandbox model on iOS does not allow one application to check for the existance of others or access public data from them. (“As far as I know” isn’t very far on iOS, so I may be wrong; just looked for exactly this one time, and it wasn’t possible back then).