I have just purchased redstick sitecad basic, mainly because it was on sale on app store for $12.00NZ. For a basic measure up tool, it works brilliantly, I used it on my andriod phone, was a little small but did the job, will be getting a tablet at some point as I think it would make it alot easier to use. I also like the it can bluetooth to lecia laser devices. The IFC export worked well, sent it via dropbox and it was waiting for me on my desktop when I got back to the office.
There is currently no documentation on how to use it but they are working on producing it at the moment. It was pretty easy to get the hang of, although it did seem to struggle with angled walls, but again I not sure if this is a limitation of the software or a limitation or my knowledge of how to use it.
I guess the best thing about it is that you get a full model that works, no more getting back to the office and finding you have missed a key dimension, or can't read your own hand writing