I'm a bit curious to know if such a thing exists, Particularly for old Mazdas.

Do scan tools for older cars exist?

I'm aware that before OBDII was a thing, manufacturers had their own proprietary connections for diagnostics, Mazda had their 17-pin socket under the hood (used until 2009, amazingly). A quick search led me to a $10 "Adapter" so an OBDII tool can connect to it.

But I'm wondering if a cheap bluetooth scantool, similar to the common ELM327 dongles exist, or anything that can be plugged into the diagnostics port to send info to a phone, computer, or whatnot, while the car is driving.