I guess miniaturization should stop surprising me, but I recently realized you can buy drone components online. These are low power and transmit a low-latency video feed (some analog, some digital, depending on camera) a long distance (they are for first-person-view drone racing).

https://betafpv.com/collections/cameras

The price is what really surprised me. The most expensive thing there is $14. There are many similar options floating around. I assume that these are priced at a premium because they are for applications where people care about shaving 0.1g.