Or if you stub in the photo APIs, what does an app do when it tries to find a photo to show and the user said "no". Should Android pretend there are no pictures? Return some fake stock pictures?
If you fake GPS data than if the user accidentally turns off location access on an application that needs it the app has no way to inform the user that it won't work well. As far as your run logging software knows you are now just running on the same treadmill for the rest of your life.
Just seems like you're likely to create situations that are confusing/suboptimal for users. Let the app know what's going on. If the app doesn't behave well in that circumstance it should be removed from the store or punished by users with poor reviews.