Ciao Gabriele, thank you for the endorsement from us too 
I wanted to provide a link to our design/white paper document, I hope people find it interesting http://ghgreenaddress.files.wordpress.com/2014/04/greenaddressp2sh2of2hd-61.pdf
In the document we describe our current design and also some improvements we are working on including making sure that we provide time locked transaction even before putting your bitcoins in your GreenAddress wallet, making it effectively zero-trust.
Thats of course assuming that you are not using the web site for full login operations as the service could be compromised but either the chrome plugin or the android application (which verify tx before signing against the electrum network) which are open source and can be inspected.
We also have some very alpha API documentation (used by all our wallet apps) which were working on polishing : this should allow integration with any third party software & hardware wallet, vending machine or ATM, etc. See http://api.greenaddress.it
Please note we are also working on risk management and fraud detection and will be providing updates as our solutions are ready as well as the market ready for adoption.
Last, but not least, GreenAddress uses HD keys both on the client and the server to avoid any type of correlations so, differently from BitGo, the privacy for the user is always ensured.
Another difference between GreenAddress and BitGo is that its impossible for a malware to get both the private keys since they never are on the same device at the same time, even at creation time.
oh, we recently added dutch, greek and qr code support to all html5 platforms including iOS, even for login
Cheers!
I wanted to provide a link to our design/white paper document, I hope people find it interesting http://ghgreenaddress.files.wordpress.com/2014/04/greenaddressp2sh2of2hd-61.pdf
In the document we describe our current design and also some improvements we are working on including making sure that we provide time locked transaction even before putting your bitcoins in your GreenAddress wallet, making it effectively zero-trust.
Thats of course assuming that you are not using the web site for full login operations as the service could be compromised but either the chrome plugin or the android application (which verify tx before signing against the electrum network) which are open source and can be inspected.
We also have some very alpha API documentation (used by all our wallet apps) which were working on polishing : this should allow integration with any third party software & hardware wallet, vending machine or ATM, etc. See http://api.greenaddress.it
Please note we are also working on risk management and fraud detection and will be providing updates as our solutions are ready as well as the market ready for adoption.
Last, but not least, GreenAddress uses HD keys both on the client and the server to avoid any type of correlations so, differently from BitGo, the privacy for the user is always ensured.
Another difference between GreenAddress and BitGo is that its impossible for a malware to get both the private keys since they never are on the same device at the same time, even at creation time.
oh, we recently added dutch, greek and qr code support to all html5 platforms including iOS, even for login
Cheers!