Thanks for the tip. I will buy this and try it out, open sourcing any scripts I can write that will assist in the extraction. Do you know of any existing tools?
https://www.sqlite.org/sqlite.html
In particular, the CSV output mode could be handy for getting query results into other programs.
You need to use the Bayer software to talk to it (I'd recommend actually installing the software rather than using the copy from the meter itself). But then the readings are stored in a standard sqlite database without any obfuscation etc. It uses some sort of hash so you can't actually modify things, but for just getting the raw numbers I didn't have any trouble.