I've had a similar thought on an accelerometer for a while now as well. They have some super cheap like, $5 ones designed for the Raspberry Pi or Arduino that I've looked at just to play with. Should be pretty easy to feed that back into the MS. I started on a Pi because I just had one in the car for display stuff, but I like the Arduinos because they don't actually run operating systems, so they don't really have bootup time. They are really just microcontrollers, not full fledged computers. That comes with its own limitations, but if you are just wanting to run some code to talk to a sensor and send that data somewhere else, they work really nicely. I tried to offload my speedometer control to a Pi Pico (essentially the same as an Arduino in many respects) because I was tired of waiting for my Pi to boot before my gauge would start working. It ran fine for a while, but something electronic failed and I think shorted on it. The Arduino Nano was even smaller than the Pi Pico, though it costs a bit more. The biggest advantage with the Arduino I got is that it will run of 12V directly, so I can wire it straight to the car for power without having to put another 5V converter in there somewhere.
I've debated going real crazy and essentially building a BCM for my car for the fun of it, but haven't gotten to that point yet. I would really like to add remote power locks since you can't lock the door till it's shut, so the car is just asking for it. I've also been looking at getting universal bluetooth TPMS sensors and piping that data into my little column display (and maybe to the MS via CAN as it could be interesting to log). If I did end up being silly and decide to try to develop my own automatic climate control (need to actually install A/C first...), that would be one more thing it could run. I need to just sit down some day and write out all the inputs and outputs I'm interested in to see what makes sense. Would be a fun side project and could maybe condense some of my wiring, but in reality it would probably just make more of a mess, lol.