These kinds of keyboards are being sold all over China (where we live) in pretty much any corner computer shop for less than US $10. I've tried them out to feel them. The keys are a little mushy but have a click. I'm not sure how long they'd last build-wise, but they're probably not for speed typists.
The biggest problem I have with these is the size. They're not as compact as I'd like--they don't fit in your pocket, unless your pocket can hold something that's a little bigger than a beer can. (For myself, I use an old Palm Thinkpad Stowaway bluetooth keyboard which folds up into a small package).
The only other issue I'd see for using it with an NIT is the power consumption. They may work fine from the NIT's micro-USB port, but I don't know because I haven't tried them personally.
Some other pro's for this keyboard: it's waterproof; probably easy to throw into luggage when you travel.