Tasker can do what your app did very easily. I use it to put my phone into hotspot mode when in the car (which the car PC then sees and uses). I used the detection of the car's bluetooth handsfree to switch over to hotspot mode and back automatically.

Tasker can do a bunch of other stuff too so has additional advantages. Please don't take this as a criticism at all - just wanted to mention Tasker since it's so powerful.