Bartenders are famous for dispensing advice along with booze, but here's one barkeep that can literally tell whether your glass is half full or half empty.

Microsoft engineers have been working on an application for their multi-touch Surface tabletop PC that detects the level of drink in your glass and automatically offers you a refill.

SurfaceWare use Surface's ability to emit and detect infrared light to gauge the grog remaining in glasses fitted with a special prism.

Bottomless boozing

The prism only reflects light when exposed to the air, letting Surface know when you've reached the optimum level to be offered a refill (apparently it's when you've got about a fifth of a glass left).

A barman can be alerted by a change in the colour of the bar counter, or Surface can dispense with human help altogether and offer you another round.

Microsoft techies have been busy testing SurfaceWare with different glasses and prisms, so we're hoping for a deployment at the Harrahs casino in Las Vegas (which already uses Surfaces in its iBar) in time for January's CES show. Strictly for research purposes only, of course.

Check out a video of the SurfaceWare app at www.youtube.com/watch?v=DG3_2lvoL8A.