Things That Seem Like They Should Be Easy but Are Actually Virtually Impossible

Getting an Odometer Reading via the OBD2 Port

There are PIDs for pretty much everything, but alas no PID for “total mileage” or even “trip mileage”. I have wanted a trip logger that syncs via WiFi for YEARS now and this weird limitation is the primary thing stopping me from building.

And like, I get it, you don’t want people to have any reason to tamper with OBD2, and “odometer fraud” seems like a reason people might want to tamper with OBD2. But you completely sidestep that risk by just not including it. How inconvenient for me.

Every couple months I’m like “how hard could it possibly be to find the manufacturer-specific CAN messages for all the vehicles in my fleet” and every couple months I am reminded why I am not a car hacker.

UPDATE: Apparently all cars after model year 2021 are mandated to have a standardized odometer PID because California said so. This actually started in phases in 2019. However this does not help me specifically as 0 of my vehicles are 2019 or newer.

Programmatically Detecting an Answering Machine

SIP is a whacky wonderful protocol that covers many many cases. Over the years it has been evolved and tacked onto to solve various issues individuals and organizations have had.

You know what that protocol does not cover? Answering machines. Absolutely zero indication to the caller that they’re talking to an automated answering machine vs talking to a human.

And reader, you’re probably saying to yourself “huh, that’s weird, but surely somewhere in the telephony stack, SOMEWHERE you can determine this information right?” And reader, I thought the same thing! But no! Nothing anywhere in the chain can deterministically tell you an answering machine is answering vs a human is answering.

In the grand scheme of things I guess this is probably a good thing? Scammers and spammers would definitely figure out how to use the distinction to their advantage, although there are many commercial products available today that can do this by having AI listening to the call and listening for the beep or whatever.

I’ll be sure to file a feature request with the phone providers.