I synchronize Zim via Git plugin. I am happy with Zim, I just would like better UI, native android, and perhaps calendar and even email integration.

I did quick search, and it actually looks feasible. Libs are available, PyQT, text file for storage, sync and storage reliability provided by Git. I even picked up name 'Lookout' :-). Now I only need the right motivation, perhaps if akonadi or k9 mail piss me off again.