OK now that it works great on a breadboard, time to turn it into a single packaged project! The Lockitron body has just enough space to fit the FONA, Metro Mini, and battery. I did need to trim some plastic off the battery holder and be a little careful with placement but it did fit!

Freewiring

The breadboard will definitely not fit inside the enclosure, so instead of breadboarding it, we use these nice silicone cover wires which are very flexible and strong. Begin by freewiring the Metro Mini to the FONA, and go through all the tests making sure the Open Sesame sketch still works.

Then add in the TB6612 motor driver, you'll need to solder directly to the wires in the Lockitron.

Run the test again, making sure the motor moves, etc!

Fitting

Then you can start fitting in parts. We covered the solder points on the bottom of the breakouts with Gaffer's tape to protect them since they're all sort of squeezed into that corner spot!

Start with the motor driver, it goes right into the cavity next to the AA holder. Don't forget to cover the battery terminals so they dont short against the motor driver!

The Metro mini fits alongside next to the motor driver, with the MicroUSB jack pointing towards the corner (with a little filing and gluing it could be a programming slot!) and then the FONA slides in right next to it too. We removed a little plastic board-slot jig that was used for the original PCB to get the FONA to sit flat

To fit the battery in, we cut off a bit of the battery housing plastic and slid the battery alongside the battery casing. The antenna is then stickered onto the battery case covering which means there's no metal around it to attenuate signal

Then cover it up with the plastic casing! Try it again and deploy onto a local door