Researchers Turn an Old Android Phone Into a Walking Robot

An old Android phone tucked away in a drawer might still have a useful job ahead of it. Researchers at UCLA have used one as the computing hub for PhoneBot, a small, two-legged robot that can follow people and get back up after falling face down.

The robot stands about 19 inches tall and weighs around four pounds, including the phone. Its hardware costs roughly $400, according to the researchers, not counting the smartphone. That’s still a project with a bit of a learning curve, but it’s less than the cost of many research robots.

PhoneBot has 13 motorized joints: six in each leg and one that lets its upper body turn. That last joint helps the phone’s camera point toward someone while the robot’s feet remain in place.

The phone handles much of the sensing and computing. Its camera helps identify and track people, while built-in motion sensors contribute to balance. A walking-control program sends movement instructions over Wi-Fi to a small computer inside the robot, which then communicates with its motors. The phone isn’t physically wired to the robot, making it easier to replace with another device.

Researchers trained the walking system in simulations before trying it on the robot. PhoneBot can walk on level ground and stand up from a face-down position. Its abilities are impressive for a machine built around a smartphone, though they’re still limited to what the research team has demonstrated.

The team tested the robot’s core functions on four Android phones, including an Honor 9 from 2017, a Samsung Galaxy A16 5G and two Motorola Moto G models released in 2024 and 2025. The three prepaid phones reportedly cost between about $50 and $90 when purchased for testing. The older Honor 9 couldn’t run one mapping feature because certain Google services weren’t available for it in the United States. So, not every Android phone will necessarily support every function.

PhoneBot can follow a person using its camera and turn its upper body to keep them in view. It can also support conversation, but that part currently relies on a separate laptop to process speech and generate responses. The phone records the user’s voice and plays the reply through its speaker.

There are practical limits. PhoneBot has no arms, so it can’t pick up objects or help with household chores. Its walking system was trained on flat ground, and stairs or uneven surfaces remain difficult. For now, it’s best understood as an experimental research platform, not a robot ready to roam around a typical home on its own.

The estimated $400 cost covers hardware, not the phone, and it may not include everything a builder needs. Access to a 3D printer and assembly tools could be necessary, and shipping or other expenses may add to the total. Putting the robot together also calls for technical skills. The project’s hardware plans and assembly materials are available, but the complete Android app and trained walking software may not be readily downloadable. Anyone hoping to build a working version should check that the necessary software is accessible first.

Using a smartphone for sensing and computing helps avoid some specialized components, which could make robotics experiments more affordable for students and research groups. The team hopes to improve the robot’s ability to move over uneven ground, add lightweight arms and eventually run more conversational AI directly on the phone. Those are future plans, not features PhoneBot has today.

A phone that’s no longer convenient for everyday use may still have plenty of processing power. Turning one into a robot isn’t a simple weekend project for everyone, but PhoneBot offers an interesting example of how older devices might find a second life—and how lower-cost hardware could make robotics more approachable.