In 1969, Gunpei Yokoi - who has Game & Watch, the Game Boy and Metroid on his resume - developed this "Love Tester" for Nintendo, a crude device that was supposed to tell how much a boy and girl truly loved each other. The pair would grab the small "knobs", talk/kiss/talk dirty to each other, whatever, and the device in the middle would pick up their heart rate and deduce how much "passion" there was between them.
It was a lie detector, basically, and was even marketed in the West as such, the ad below in typical cynical fashion calling it the "Lie/Love Detector".
Complete rubbish it may have been, but it's also a machine made by Nintendo (and the creator of the Game Boy, no less), so it's more fondly remembered than you'd otherwise suspect. In fact, it's recently gone back on sale, this (presumably) licensed replica going for USD$55.
It may not be the real deal, and it may not actually test your love - or even your vitality - but that sure is a nice box to have on the shelf if you're a Nintendo collector.
If you're wondering, the picture at the top of the post is the replica. All other shots are of the original device and its original packaging.