- I'd incorporate touchID, I've used it in iOS and it's easy to add.
- One feature I'm thinking about for my iOS apps is using the Apple Watch as a 2nd factor auth mechanism. I haven't looked into the feasibility of it yet though and probably not many people have smartwatches
- After the user writes down the seed when setting up the wallet, challenge them to verify their written seed. I think this is how Electrum works, try that out
- BIP standard is a good idea for the seed, but try and mention other wallets that the seed can be used in, for reference purposes
- Multisig is definitely the winner here, but I'd go farther, really look into trustedcoin API
Basically my preference for bitcoin software is like this:
1. If there is a bad update to the software, I feel safe that it doesn't matter too much because there is a secondary signature needed to approve a transfer
2. If the software is discontinued or I want to stop using it, I feel safe it doesn't matter because I can restore from a seed elsewhere
I appreciate safeguards to the device like the touchId etc, however there's a tricky balance there of security vs usability. I think using the touch movement pattern is a great idea for a backup method and touchId can be the primary method.
Currently, you can always fully recover all your coins from the seed values you back up during the wallet creation.
Our wallet is built on BIP standards.