Since 2013, Edward Snowden has been advising people and creating software. The Haven app he’s been working on  l interesting, and given I’ve got a spare Android smartphone, I might try it in my home office!

Designed to be installed on a cheap Android burner, Haven uses the phone's cameras, microphones and even accelerometers to monitor for any motion, sound or disturbance of the phone. Leave the app running in your hotel room, for instance, and it can capture photos and audio of anyone entering the room while you're out, whether an innocent housekeeper or an intelligence agent trying to use his alone time with your laptop to install spyware on it. It can then instantly send pictures and sound clips of those visitors to your primary phone, alerting you to the disturbance. The app even uses the phone's light sensor to trigger an alert if the room goes dark, or an unexpected flashlight flickers.
Source: WIRED

Update: more details in an article at The Intercept