The arduino, the open source microcontroller board, has had MQTT support for a long time in the form of [Nick O'Leary's arduino client]. It does however require networking support which has traditionally provided by an add on shield, which increases the cost of the system. The [Nanode] is an arduino compatible board which includes network support and can be built for approximately the same cost as a normal arduino board. It's still a work in progress, but is definitely worth a look if you want to use low power MQTT capable sensors/controllers. [Nick O'Leary's arduino client]: http://knolleary.net/arduino-client-for-mqtt/ [Nanode]: http://nanode.eu/