Okay a 2 second google search! 8P
Its called Chindogu.
The english name is "Unuseless".
And a rule: "humour must not be the sole reason for creating chindogu"
You'll see its actually very hard to make one and follow all the rules.
Here are pages with info.
Chindogu history
Wikipedia
The site above is an example if Chindogu.
Have fun finding more or inventing your own. 8P