Thanks for your interest! As far as my research went, Assetto Corsa Rally uses the same shared memory feature as Assetto Corsa Competizione, with exact same memory fields, at least for physics and static info, in the exact same shared memory file locations, so if you can find a tool to do telemetry on ACC you can use it for telemetry with AC: Rally, and they may be better/more mature alternatives than my hacked together attempt, with proper GUI/data logging/UDP support. I'm keeping mine's distribution limited to an accessory to my overlay to keep complexity of the source code down.
ah thanks a lot, that might be a good approach as well. I found your "hacked together attempt" quite workable and came up with a simple python script yesterday for recording the raw udp stream, and later another one for splitting it into segments (= restarts; I was doing experiments around the first few corners), and then visualizing several such segments aligned with each other for comparisons. It's amazing what information just a speed/rpm readout can tell one. I totally get though, if that seems like blowing up the scope of your tool, and I'll have a look at the ACC-approach. Thanks for pointing me in the right direction!