I generally don't do this (disclosure: the inventor of this product and I worked together at one of the seminal Silicon Valley startups), but I know enough of you have opted for iPads and you'll see me doing more coverage of the photographic aspects of that product in the future, so...
Touchfire is a clear overlay that makes the on-screen iPad keyboard feel like a real keyboard. I don't know how to say it any simpler. At one ounce and iPad Smart Cover friendly, it's sort of a no-brainer if you do any significant typing on an iPad, as you don't need to add an external keyboard to your kit. The screen area is still visible and active underneath the transparent plastic that provides you the tactile feedback, and you can easily flip away the Touchfire if you need to.
We're slowly getting photography software on the iPad that takes advantage of keyboard access. For example, imagine a scenario where you're in the field and you've imported the contents of your SD card directly into your iPad, at which point you use a Lightroom Lite type of application to do your edits and entry of your metadata. A keyboard would be a big help in that instance, but it sort of defeats the purpose of going light with an iPad if you end up with an external keyboard that makes the combination as big as a MacBook Air. Thus, I can see the Touchfire's utility being of interest to us photographers soon.
Since it's currently a Kickstarter project, the Touchfire is not yet available, but I have little doubts it will jump over it's low funding barrier and become real, very soon. If you want to be an early adopter, you can check out the story at touchfire.com and sign up for one of the very first units (US$45).
As I wrote, I don't usually step outside of a narrow set of boundaries in terms of product coverage, let alone one with a potential conflict of interest. I always disclose when I do, as I am here. The inventor and I go way back, and we've had discussions about missing software products that we may yet just act on. I'd love to see Steve go over the top of his Kickstarter campaign, mainly because I want to get my own Touchfire sooner rather than later.