If you're running code that executes in Springboard, this should be fairly simple. Get SBApplicationController's sharedInstance, then get the SBApplication you're looking for with the applicationWithDisplayIdentifier: method (or using whatever method you choose). The SBApplication class contains properties for path, containerPath, and bundle (among many others), one of which should be what you're looking for. I haven't tried this myself, so I can't guarantee it'll work, but based on a quick glance at the Springboard header files (you can take a look here, or dump the header files yourself), it should work.
On the other hand, if you're not running from Springboard (ie. if you're making an actual App Store-style application), then you may be out of luck. You could look into inter-process communication with Springboard and see if something can be done there, but it'd probably be more trouble than it's worth.