I'm looking to use the CMMotionActivity for iPhone 5s's, but also want to be able to use similar functionality on older iPhone's, is this possible?
Could I create a less accurate alternative maybe, by tracking GPS and not using the M7 chip? Any advice/tutorials/sample code?
You can create your own algorithm which will utilize accelerometer data and estimate number of steps taken. Its not as accurate and its not a good idea to have 2 separate logic in the same app.
In case, you want to give it a try, check this answer..How to count steps using an Accelerometer?