Fake GPS location for specific app on iPhone
I have not tested any of these methods, but a quick search reveals the follwing apps / hacks that claim to do this:


iSpoofer - Claims to "Easily simulate any GPS location on your iPhone/iPad/iPod". 
iTools - Claims to "Perfectly fake GPS location on an iPhone / iPad".


Source: How to fake a GPS location on your phone

A more complicated way of doing this manually, without installing any app is also described here: How to Fake Location on iPhone Without Jailbreak.