PhoneBot turns a spare smartphone into the brain of a $400 open-source humanoid

PhoneBot, a small bipedal humanoid described in a paper posted to arXiv on October 6, 2026, uses an ordinary smartphone mounted on its torso as its main sensor and computer. The authors, Ruochen Hou, Quanyou Wang, Daniel Koh and Dennis W. Hong, are from UCLA, according to reports on the work; Hong leads the university’s robotics lab RoMeLa. The hardware and software designs are open source.

Excluding the phone, the parts cost about $400, according to Korean and US press reports. The robot stands about 48 cm tall and weighs about 1.8 kg with the phone.

What does the phone do?

Almost everything above the legs. The paper’s abstract says the phone provides the inertial sensor, camera, wireless connectivity and onboard processing used for perception, control computation and interaction with the user. Press reports describe the phone running the control software and sending commands over Wi-Fi to a small onboard board that drives the motors. The 13 actuators are six per leg plus one that rotates the torso.

The design choice is about cost and reuse. A recent phone carries a camera, an IMU, radios and a processor that would each cost money and integration time as separate robot parts. Swapping phones also upgrades the robot’s compute without changing the body.

What PhoneBot is not

It is a research and teaching platform, not a cheaper version of a working humanoid. At 48 cm it is closer to a robot kit than to the machines in our humanoid price guide, such as the $15,000 Unitree G1+. The abstract describes no manipulation and reports walking and interaction results without quantitative metrics. Its value is access: a platform that a school or a single student can build, break and rebuild, with the design files available at the project’s website.