If you're worried about elderly parents spending all of their money and they are accepting of your help, there's a few things you can do.

Freeze their credit. Open a new bank account that will be their spending money, transfer money into it on a schedule. Set up regular bills on autopay so they get out of the habit of mailing checks (lots of mail gets sent to elderly ppl making it seem like it's gov and a response is required). Set up MDM on their phones and computers. Get them a low limit credit card.

You don't have to do it all. Credit freeze, MDM, and bill pay are probably the biggest and easiest to get consent to.

For better or for worse, the category of “software that silently listens in on calls” is non-existent due to OS limitations. Generally sounds like a lot of work and computation for a very rare situation.

Lowtech solutions would just be taking the (bank) key away from the elders, just like they’d hide my grandpa’s literal car keys when he was 70 with dementia.

Tbf the bank thing is already a thing in a very limited capacity, but at some point the scammers figure out a bypass. The phone call thing is interesting but I wouldn't want an AI having all of my phone calls and it'll be hard to convince people to use it since everyone thinks they won't be scammed - better spend that time educating about scams instead. It'll also be much easier to bypass than the bank detection thing as a scammer can easily get access to the product.