This is a nice idea and good implementation. It's even asthetically pleasing.

The only thing I worry about with applications like this, is it requires me to trust you (not that I don't). At any time you could release an update and acquire people's keys could you not? You state your issue with that concept with regards to steemconnect etc, and it's a legit gripe. Keeping the keys local, and accessing through the browser is better, but does it really solve the trust issue?