The May 2009 issue of Wired magazine had a write-up about spy gear. You can read it online. The item on their list that really attracted me was the pocket grappling hook (although the bulletproof dress shirt is pretty cool).
The collapsible aluminum and steel grappling hook is small enough to be called pocket sized, it can act as water proof container and only costs $30.
Holy crap, Batman! It's perfect. A must have.
This isn't a grappling hook for swinging from. It's designed for snagging trip wires and tearing down barbed wire. For something that I would actually consider climbing with check out Capewell's Retractable Grappling Hook. That's something I would actually expect Batman to use for scaling buildings.
Of course, we all know about Batman's secret superpower: his grappling hook. It's way too small to make any sense and to pull him at those speeds! Although, grappling guns that amazing don't actually exist, there are line launchers such as the one in the ResQmax kit. They don't seem to come much smaller than that and it just launches the line, either by compressed air or a small rocket. If you want to be mechanically pulled up you need a completely separate tool. If you thought the grappling hook launcher was big, you'll be very surprised by the size of existing motorized hoists, or ascenders. A company started by some MIT alumni, called Atlas Devices, builds these. They are simple (apparently the prototypes were built out of power drills) but big and probably pretty loud.
The really long, video about the pocket grappling hooks by Maratac:
The ascender by Atlas:
Oh and if you want to read some more facts about grappling hooks check out the eHow articles (don't forget the Related Articles on the side)