I'm trying to find an easy way to make a battery powered arduino wake up from a remote.
There are plenty 1$ ble tag devices sold as key trackers, which can be connected to from your phone and triggered to run a buzzer. I thought I might be able to repurpose one of those and connect its buzzer output to an arduino's interrupt. These devices run easily on a coin battery for months or years so it might be a good solution.
I triggered their alarm, but they don't have a service where you can disable the disconnect alarm (an annoying beeping when the connected device gets disconnected)