I've been after something like this for quite a while, so when I spotted it at the local auto parts store (in this case, Eastcoast Auto parts in East Bentleigh) I grabbed one straight away.
It is a small, lightweight, battery powered mini rotary tool. It's about the same size as a parcel marker, and not a lot heavier. It's size can be judged from the photos, they are AAA batteries in the pack and the handle is just big enough to take two.
It is unclear from the packaging whether this is a rotary or reciprocating style of engraver. After studying the tool, I reckoned it was of the rotating variety. Once in action, I confirmed that it was, indeed, a rotary tool.
It's not particularly cheap, I paid $35 for mine. It is also a single-speed unit, so you can only use it at the standard, quite high, revs. I estimate it spins at about 12000 RPM, but I have no way of verifying that, nor does it tell you on the pack.
On the plus side, it is very light yet has a nice quality feel to it. The body is a fairly thick-walled aluminium tube.
The engraver comes with one very small engraving bit that would be suitable for, well, engraving! I had some narrow-shafted (2.3mmØ)Dremel bits in my toolbox and these fitted fine. They are of the grinding variety, rather than the cutting variety, and my tests were of the melting-rather-than-cutting variety. For all that, it did a good job and the bits didn't get clagged up despite the melting of the plastic. I will get hold of some cutting bits and see how they go.
I'm quite happy to recommend this product even at this early stage of use simply because of its small size and cordless versatility. It's something I can leave lying around the workbench and just pick up and use without having to worry about power points and cords draping over the workbench and damaging delicate model parts.
I have since found a set of drill bits that fit this device. I bought them from Carbatec at the 2012 ModelExpo in Melbourne. They are very fine drills, but they have an enlarged shank that fits the engraver perfectly. I have used them many times and they have significant advantages over the hand-twisted type of pin vice.
The most obvious advantage is that you can hold the drill very steady while you do the drilling. The tool itself isn't being wobbled around while you try and spin the shaft with your fingers. Another advantage is that the speed of the drill makes drilling holes quick and accurate, the bit doesn't tend to wander at all, it just bites straight away and drills. This does mean you have to be in the right spot to start!
You can also use the sides of the bits like a milling machine, using gentle pressure so you don't snap them.
At around $15/$16 a set, these are well worth the investment and make the rotary engraver even more versatile.