Maybe the most obscure GBA game ever made has been preserved - an Australia-only blood sugar tester

gamesradar.com:

One of the most obscure GBA games ever created has finally been preserved: the Glucoboy, a combination of game cartridge and blood glucose tester that was designed to help encourage kids with diabetes to stay on top of blood sugar monitoring.

The Glucoboy was the brainchild of an inventor named Paul Wessel, whose diabetic son was a Game Boy enthusiast. Wessel believed that games could help kids push through the hassle of regular blood testing, and began his efforts to bring the product to market in the early 2000s, but was only able to secure funding in 2006 - $1.5 million from an Australian investment bank - which held the device's release back until 2007, when the GBA itself was rapidly losing relevance against the DS.

An excellent video from Kelsey Lewin, now the co-director of the Video Game History Foundation, breaks down the history of the device's development and the content of the included games. In short, there are two major games included, one of which is a JRPG-style adventure that gives you items for regular testing.

The device sold around 70,000 units according to Wessel, which was enough to attract the attention of pharmaceutical giant Bayer. Bayer bought out Wessel's company in 2008, and released a similar device called the Didget in 2009 - but not before destroying all unsold stock of the Glucoboy. Retail Glucoboy units, then, are among the rarest devices in all of video game collecting, and preservationists have been searching for a copy of the game for years.

Now, it seems, a working Glucoboy has finally been found and dumped, and the ROM has been uploaded to the Internet Archive. I won't directly link to it here, as the upload is technically piracy, even if it's not infringing on a particularly