I also figured it out some time ago. You get the robot secret key and serial number when you log in to beehive.neatocloud.com and request https://beehive.neatocloud.com/dashboard
I've written a powershell module where I exposed the entire api (as implemented in the android and iphone app), complete with login. I've yet to upload it to github but I can send it to you if you're unsure about the beehive part.
@roberto Awesome to see you make the API public and official even though it seems that you're just making the endpoints "official" and pretty much identical to the API resulted from reverse engineering efforts. Any chance you (as in Neato) would consider allowing us to switch to our backend server, essentially replacing your cometa.io server (cometa.neatocloud.com)? And on a sidenote, to get access to the developers portal and API through your site, you have to accept to your new terms, yet you've made the libraries public on github. 
As for replacing the cloud server, I don't think it's possible without rooting the robot. The first thing it does when it's connected to the internet is to start an HTTPS Comet session (long polling). The robot will kill the connection immediately if you try to MiTM it with a selfsigned certificate and there is no way to install new certificates on the robot. If anyone has opened the robot I'd be interested in pictures of the motherboard, especially of any pads labeled JTAG.
I also figured it out some time ago. You get the robot secret key and serial number when you log in to beehive.neatocloud.com and request https://beehive.neatocloud.com/dashboard
I've written a powershell module where I exposed the entire api (as implemented in the android and iphone app), complete with login. I've yet to upload it to github but I can send it to you if you're unsure about the beehive part.