So my ten year old daughter wanted to build a keypad enabled electric lock for her bedroom "to keep her little brothers out". TLDR: go here and solder.
We picked up the Jaycar Arduino Compatible 16 Key Touch keypad module cat XC4602, which is based on the TTP229 capacitative touch sensor IC. The board's by duinotech, and the only discernible numbers are 1003010 on the board, and 8229BSF on the IC.
There's a downloadable Arduino demo on the Jaycar page, but we didn't have any luck with it.
To get all 16 keys working, we followed the helpful instructions posted by this guy. Yes, it does actually seem like you have to solder at least jumper 3 (yellow link on his post). That's the only one we did.
Then he's got a link to his code, but it's hidden down the bottom of the page. Direct link. You'll need to create yourself a Dropbox account to be able to download it though. The only other gotcha is that his sample code writes to serial at 115200 baud. Make sure you set your monitor to the same or you'll just get rubbish.
After that, it's happy days. Just follow his wiring, and sample code. I figured I'd put this post out there pointing to his blog because there's a number of other posts out there about this IC that were much less helpful.
Aside, we're using the Jaycar Electric Strike EL-973 (fail safe version), Jaycar cat LA5081, for the lock mechanism. It needs 12V to activate, so I figured we'd drive it like a motor with an IRF520 mosfet. It works a treat.