This is a device to wear on one of your arms. It can be purchased from most "reputable" traders. A favorite item of bored deities with too much time on their hands, who are looking for new and creative ways of
irritating pleasing their heroes.
Contains many things which are highly valued by heroes (except a built-in supply of beer), like a health monitor to see if they are dead, a full list of inventory items including broken artifacts and space taken up by tribbles, a list of the equipment and weapons currently being used, and maps to guide them to the nearest tavern town, and lots of pretty buttons and sliding things that are fun to play with, but beyond the mental abilities of the average hero.
Also extremely effective at showing the location of marauding monsters sneaking up behind you, although simply turning around is likely to be just as effective at spotting them. This device has been known to occasionally cause the untimely death of the wearer, when they spend too much time checking their vitals on the device instead of paying attention to the goings on around them.
I recommend it if you can get your arms on it, or rather, get it on your arms.