Still a work in progress but feedback gratefully appreciated.
https://github.com/ianpurton/StampAndroidSo basically Stamp is mobile app HD wallet generated from a seed (currently electrum) that can then create master public keys and sign TX's. (Stamp never holds coins).
To do this it simply scans a QR code. For the user, this is very simple to use.
Example...
Online market place using multi sig for escrow.
1. On signup the market place can ask for a MPK (Master public key) via a QR code.
2. Stamp POST's back the MPK via HTTP.
3. Site can then generate any number of P2SH addresses.
4. To sign a Transaction site generates a QR code.
5. Stamp scans the code, grabs the TX using HTTP get, signs it, POST's it back.
Another Example
Online wallet
1. On signup wallets requests MPK via QR Code.
2. Stamp sends it one.
3. Wallet creates Bitcoin P2SH addresses.
4. When user wants to send a payment they have to scan the QR code to sign it.
Poor mans Trezor.
If anyone would like to help me out with this or provide (constructive) criticism, fire away.