Endoscopic camera

I've not used this but its an interesting tool if it works for less than 20 bucks. Just hook it up to your smart phone and take a look inside a cylinder.
https://deals.slashdot.org/sales/en...erfeed&utm_campaign=endoscopic-android-camera

They're pretty cool. I like a cheaper ebay version better. You want to be aware that the cord doesn't hold its shape like the expensive "inspection cameras". When feeding it down inside something you have to twist and flop it around into hopefully a useful position.
Older laptops struggle a bit with the higher resolution settings but I wouldn't look at anything capable of less than 720P. Lower resolutions like VGA look very crummy. There's little point in using the thing if you can't make out what you're looking at. I've had a cheaper lower resolution one and a newer higher resolution one. The cheaper one was useful but the other was just so much better for about the same price. They're pretty neat and occasionally useful. Used one to spot a burnt valve on a 4.6 through the plug hole. The optional 45 degree mirror endpiece is a nice add-on some versions offer.