ZincTrumpet
I had a quick look on my iPad and to be honest it seems like a simple 4 track audio recorder.
There are many similar apps for IOS which are cheap or free. I use LoopyHD which is $3.99 currently but I got it when it was on sale for less.
Even the free Apple Music Notes which admittedly only records a single track can then automatically recognise chords, add bass and drums and send the result to Garageband.
There's no way I would consider paying a subscription for Momentum and I cannot see myself using even the free version so I have uninstalled it. It should be free for anyone who owns or subscribes to Sonar.
One point made over on the AudioBus forum is that users of IOS Z3ta+ feel that it was abandoned by Cakewalk and wouldn't want to get stung again with Momentum.
Momentum is not a single app on a device. If it were, I agree with you, it would just be a free app.
Momentum works on every device you own, and any DAW you use. With automatic cloud sync, your musical ideas and snippets are always available.
Some people are using Momentum to record ideas on the smartphones and later drag-drop them into their DAW.
Some I spoke to are using it as a plug-in in one DAW to make beats, recording those beats into the Momentum plug-in and then loading the plug-in in their primary music production DAW.
Soon we hope to add inter-app audio and more collaboration features that will open up even more possibilities.
The bottom line is this—musicians we spoke to often complain they don't have time to make music. And then when they find the time, they just don't feel like wrestling with their DAW just to get an idea down. Momentum is attempting to solve that and help musicians get their ideas out and see them through.