Wikipedia says "Springstock" or "Pogo Stick".
http://de.wikipedia.org/wiki/Springstock

Top tip: look it up in English Wikipedia, then change the language using the menu on the left hand side.

Ich kenne dafür auch die Bezeichnung "Hüpfstock" ...

And I have never ever seen one here in Germany...had one way back when, and none of my German friends even knew what they were. They had some kind of wooden "thingy" they used, but not at all the same thing. When my own (German) children came along in the late 70s, early 80s, even those things were nowhere to be found.

Just for the record, it should be two words in English.

Oberbegriff: Hüpfgeräte

Pogo Stick = "Powerizer"?
https://www.google.de/search?q=Powerizer&clie...

Übersicht über Hüpfgeräte:
https://www.google.de/search?q=H%C3%BCpfger%C...