Anyone tried any of the following yardage helpers on the course?

1) Cheap scope style (<$30) - estimates yardage based on height of pin in viewfinder.

2) Handheld Laser-based rangefinders (eg Bushnell Pro Tour approx. $500) - measures laser beam bouncing off target (eg. flag)

3) Handheld GPS device attached to Palm or Handspring PDA (eg. SkyGolfGPS approx. $600) - uses GPS satelites to determine golfer position relative to pre-determine spots on the course.

I'd be interested in hearing feedback on any of these devices.

I'm always looking for new golf toys for the bag. And yes, I know I can't use these in tournament play.