The ESP32 WiFi robot is a shrunken-down version of the ZeroBot (https://www.thingiverse.com/thing:2800717). Instead of a Raspberry Pi, it is powered by the similarly popular ESP32. Despite its lower processing power, the ESP32 robot has a ton of features. It streams color video over WiFi, runs on a small LiPo battery and can be controlled accurately from any web browser. With the 4€ Esp32 and a 3€ camera, it's also really cheap.