Very hard to compete against Push as Ableton refuses to document their nightmare of an API. Even with Push source code decompiled, it's very difficult to make sense of it all.
Have a look at pushbase and Push2 to look at Push source code.
A starter kit I use when bootstrapping projects: https://github.com/R9295/ableton-live-control-surface-starte...
To the best of my knowledge, this is as far as it goes. The blogs and articles I found are mostly out of date as Ableton has two versions of it's API and blogs mostly use v1. I wouldn't work on anything serious using v1 of the API
Many controllers, including Push use v2 as it's allegedly simpler and more featured. I talked to a person working at Native Instruments and they also told me that their experience with the API was a nightmare.
Does that seem correct to you? And if so, with some amount of reverse engineering work, shouldn't it be possible to send those same pixels over to an iPad app that pretends to be a Push?
(It wouldn't be the same without real pads/touch controls, of course, but it might form the spine of a pretty good remote control app?)