Resources for multisignature transactions?
blocktrail has a 2of3 HD Multisig Wallet API, it's setup like: 
 - the 1st key being your primary key to use
 - the 2nd key being a backup key you store offline and 
 - the 3rd key being a cosign key owned by blocktrail

it only supports bitcoin and bitcoin testnet atm though ...

https://www.blocktrail.com/api/docs#payments_overview