The Tricorder Mark 1 is, for all practical purposes, nearly identical to the device that we see in Star Trek, with the possible exception of being unable to reliably distinguish a Klingon from a Romulan. It's a self-contained, portable sensor system that can measure ambient temperature, humidity, air pressure, magnetic fields, surface temperatures, colors, ambient light level, ambient polarization, acceleration, direction, distance (ultrasonically), and of course it has a GPS receiver.
I dunno about you, but I desperately want one of these. The good news is that it's all open source (hardware schematics, board layouts and firmware), so you can build one yourself. If you can wait a bit, though, Peter is currently working on yet another version of the tricorder that he says "may be an initial model that could be mass produced, and that folks could have in their hands."
Until you get a Tricorder in your hands, you'll have to make due with just watching it in action in the video below. And we'll definitely be keeping you up to date on this one.
The phaser should be next.