bar ride or grip ride, depending on where your feet are on the bars. there's also the Scurfer named after brian Scurra. that one is a one footed bar ride, basicly..
I can't do this trick anymore and am actually scared to try them. (yep, pvssy!)
but when I could do them, I learned in baby steps.
1. learn to hop over the bars so your sitting on your crossbar.
2. learn to hop onto the bars/grips
3. practice balancing while your bike is leaned against a wall.
I remember standing on the pull up bars at the local play ground as well to get a feel of balancing on a skinny bar. but it's much different when your on a bike and rolling..
once you can hop onto the bars with your feet, the next thing to do is let go of the bars and stand up. lean forward....falling backwards SUCKS.