They're called PPT's. we use them at Virgin Blue on the 73 and EMB's. They work well, unless the batteries are starting to run down, in which case the push is extremely sluggish.

One thing to note, in Australia the push back is done by an Engineer. (You can't call them Mechanics as they can get a bit pi$$y) They stay with the aircraft until the engines are started and you confirm everything is ok.

It's a very different experience from the rampers in PHL wearing ankle bracelets, that I used to deal with in a previous life.