According to Thingsquare, Tado is using their firmware [1], Mist, based off of the open source Contiki [2]. This is pretty cool, as it enables a ton of features like over the air firmware updates or running your own applications. I'm especially curious how they added bluetooth and ibeacon support into this.

[1] http://thingsquare.com/customers/ [2] http://www.contiki-os.org/