I recently got a Thermal Master P1 infrared camera attachment for my phone. The goal was a house project, but it's also a great toy, especially with the kids. Getting a room pitch black but still being able to 'see' with the phone was fun for a bit. The real fun, though, was in exploring to observe all these thermal properties we'd never thought about.

Here's my selfie:

Light is warmer, dark is cooler. My glasses aren't cool, they're just IR-opaque. I already knew cheeks and noses were squishier than foreheads, but it's neat to see that in coloring.

Here's my 4yo, outside in ~30F weather:

The patterns are clearer, especially at the edge of the cheeks.

Here's a different angle:

The gaps in the hair are neat, and you can see the bow on her headband clearly.

Here's the cat:

This all makes sense in hindsight, knowing that the face is less furry and that there are shifting parts in the body fur, but it's neat to see.

The kids were excited about how this lets you see back into the past. Here's heat-fingerprints on a window sill I touched:

The print from one socked foot and one bare foot:

A stand mixer that had been running:

A car that had been sitting for a long time:

One that was cold to the touch, but apparently had been run recently:

Less fun but more usefully you can also see where buildings are losing heat. I'm planing to take it out Sunday morning when it's ~4F here and assess our house, but in the meantime here's a nearby house losing heat through its basement:

If I look very closely I can just make out the framing inside the wall. I'll try this again when it's even colder, and if I'm lucky I can get a bunch of pictures showing where the studs are throughout our exterior walls.

I do wish there were a way to connect the sensor to modern image processing algorithms like my phone uses for its regular camera. Combining the information from several shots in quick succession could give much higher quality, and I feel my eye doing this automatically when watching it live on the phone screen. I guess I could take a video and then post-process?