This is a crude case and chain adapter for LowPowerLab's GarageMote:
The case provides full access to all the necessary ports and connections and the light from the LED is visible through the case, depending on the material/color used. The case does not snap or screw together, the intention is to glue it together with a small bit of super glue on the corners. A bit of filing/sanding may be necessary to get a nice tight fit and open up the programming port. The GarageMote I/O board is a tight fight on my printer, a bit of filing on the edge of the PCB can make it easier to install.
The chain adapter is for garage door openers using a chain drive, obviously. The magnet provides quite a bit of adhesion to the chain on its own, this adapter keeps it in place and the fingers are intended to snap around the roller to provide an additional mechanical attachment. Depending on your chain, the fingers may not fit in the narrower gap between the inner plates, they only fit between the outer plates for me, so it can only attach to every other link.
Please note, at the time of posting, I have not yet deployed these prints, so I cannot vouch for the longevity of this solution, any magnets falling from the chain are at your own risk.
UPDATE (2017-04-27): Added additional chain bracket w/ shorter fingers for slightly slimmer chains.
UPDATE (2017-04-30): Added sensor pylon and completed project. Pro tip, when you glue the case together, put a dab of hot glue on the antenna, it sucks to crack it open to reattach if it breaks. Note that the pylon is half filled towards the top to keep the sensor against the closer edge. Shine light through to adjust the sensor height to the center of the magnet. Double sided tape on the base holds the pylon in place and holds the sensor at the preset height. I spliced into the control wire and used wire nuts to hold them together, this was easier than trying to feed two wires into the opener. Aluminum tape keeps the sensor wires securely away from the chain and everything else is held in place with zip ties. GarageMote works great on my Craftsman opener!