Looks OK, and I like the concept of combining cold storage to secure large sums of money with a hot wallet for daily spending.
However, considering the fact that it's closed source and from a fairly unknown developer, I would not trust my money with this. Especially with large savings, I will only trust that to something I can either 100% understand and verify myself, or that the general public (and in particular, other independent developers worldwide) can understand and verify.
I hope the developer will make this open source, as I think it's definitely a step forward in term of usability, and finding a compromise between ease of use and strong security.
Thanks for your interesting in our project.
We already opened android version's source code on github :
https://github.com/bither/bither-androidCurrently we are working hard on Bither iOS v1.0.1, and we will commit the source code ASAP :
https://github.com/bither/bither-iosSo you should hurry to commit your source code. I'm watching.