A Twitter user found himself perplexed today when he opened an older electrocardiogram measurement instrument and found the components belonged to a Game Boy Advance.

The instrument is made by German company Medical Imaging Electronics and uses a wave produced by the ECG to electronically control a separate recording or imaging apparatus. At first look, it seems like any standard medical device. When opened, it’s revealed that the device’s screen and electronic parts belong to a Game Boy Advance, deconstructed and embedded inside. The Verge has contacted Medical Imaging Electronics for comment.

A medical device with a Game Boy inside might seem bizarre, but it’s not that uncommon. Before single-chip computers like Raspberry Pis were popularized, the Game Boy was often used as the primary cheap, hackable alternative for controlling and programming a variety of things, like sewing machines or a sonar for finding fish up to 65 feet underwater.

In particular, the idea of using a Game Boy for electrocardiograms has been around for decades, as shown by this patent filed in 1997. The patent outlines the perks of integrating a Game Boy in electrocardiograms, including modular functionality, portability, stability of the system, immediate access to data without additional bulky hardware, ease of use, and lowered cost.

There’s not as much of a need to mod Game Boy units nowadays, but it is pretty cool to see that even in dated machines, hacked hardware hides in plain sight, in places you’d never think to look.