A homemade thermostat up in the basement rafters controls the heating in my home. The smart bit is the radio frequency communication that connects it to a remote temperature sensor.
This compact PCB interfaces a low power MSP430G2553 microcontroller with a Nordic NRF24L01+ 2.4 GHz radio frequency transceiver module. It's well adapted to serve as a wireless sensor node, but has enough I/O options to be put to use wherever a small microcontroller is required. PCBs now available from Tindie!
I have a MacBook Air with an Intel i7 core running OS X Lion 10.7.5. Booting linux from a flash drive was not straightforward, to the point that when I finally got it working I laughed with surprise. Evidently doing such things is not part of the one true Apple way. The instructions were cobbled together from from here and here with a fair bit of trial and error. Needless to say, the procedures documented on the Ubuntu website did not work for me.
A digital stirring hotplate in decent used condition will set you back about $250. I paid a fraction of that for one with a broken heating function. The problem turned out to be nothing more than a duff switch.
When I ordered some NRF24L01+ boosterpacks from the 43oh store, I asked for a couple of MSP430 Launchpad v1.4 PCBs. These are legacy boards kindly provided by TI (thanks LariSan!) It was fiddly soldering to the tiny 0402 pads since my components were all 0805. The LEDs were especially tricky. But they both turned out OK as you can see. Here they are (alongside a genuine Launchpad on the left) running the breathing LED demo from the OSX Launchpad toolchain.