Stefan designed an IoT enabled, compact and modular, 4-wheel drive robot platform powered by ESP32. It is controllable over WiFi and BLE.
As controller board an ESP32 Thing board is used this can be programmed by the Arduino IDE and allows even OTA updates. It isn’t the cheapest but offers a compact size and includes a LiPo charging capability (Which I managed to blow off by attaching the LiPo in reverse polarity L). As sensors the robot contain a BN0 055 absolute orientation sensor, a rotation encoder for both sides, four proximity sensors in the bottom (line follower, gap detection) and an APDS-9930 proximity sensor in the front to “see” obstacles. Of course a beeper and 2 head light LED’s are not missed either.