There are many different Ableton Live controller apps for iOS - from powerful Touchable app that mimics Ableton devices interface and allows you controlling literally every function of Live to flexible modern-looking Conductr.
Though if you are familiar with Ableton midi controllers you probably know very well Novation Launchpad - it is pretty cheap (comparing to Ableton push) midi controller designed to launch clips in session view but with new scripts it also acts as matrix-style midi notes keyboard (like Push or Maschine Jam).
Based on advanced Launchpad script - developer Alexander Nowak has made iOS app that repeats functions of Novation Launchpad on a touch screen of an iPad or iPhone.
And with the recent update the app brings Apple Watch support that shows part of the layout but still allows to play some notes/launch clips.
Launch Buttons - control Ableton Live with Apple Watch, iPhone or iPad
8x8 clip launch grid
8 scene launch buttons
16 freely-assignable knobs
Low-latency MIDI communication over Wifi
Color coding like on the Novation Launchpad Pro
Freely-assignable transport controls
Works with Launchpad95 (free) and Launchpad Pro95 (Plus)