I’ve inquired about the app issue on the Android and will let you know what I hear. As for cadence based on the accelerometer, there are two issues: 1) it’s not very accurate, as it is based on getting a signal and sending it back etc. and 2) an external cue like the metronome is more useful in helping you maintain a steady cadence. Studies have shown in patients with balance issues (Alzheimers, Parkinsons etc) that the external cue helps them walk with more balance - http://www.ncbi.nlm.nih.gov/pubmed/9465340 In my. opinion, this transfers over to the use of an external cue in running and walking as opposed to feedback from footfall (or motion) when trying to maintain a steady cadence.
I’ll get back to you on the Android app.
Certified Chi Running and Chi Walking Master Instructor