Since the calendar has already been mentioned, I'll drop another of my tools.
I check my pockets every time I leave a space, and confirm I've got Wallet, Keys, Phone. I do this at any transition: Leaving the house, a taxi, the office, a plane.
Got kick started into the habit when I lost a big (for a kid) chunk of money. Felt so bad that I started the checks, and haven't lost any of those three in many, many years (ง’̀-‘́)ง
When I encountered a similar situation I tried with the ikea speakers (Sonos Based) and I couldn't get them to work without the sonos app, so I returned them.
I figured that a solution could be having, in each room, a mini-pc (RPi or similar) running RuneAudio and a set of speakers connected via audiojack.
I tried with 1 room and the proof of concept seemed to work, but didn't invest on getting the rest of the house work.
In the end went for a couple of portable Bluetooth speakers to have floating around the place. Cheap and simple
Right after they sign an investment agreement with Envision? A bit sus...