Put simply, this is this generation's Polaroid system and it's very well executed indeed.
As so many of us carry smartphones, Fujifilm have come out with a great way to turn those pictures into physical prints and very fast, too. Just connect via Wi-Fi and using the application you can print photos.
Physically, the unit is quite fat-feeling, so it's not likely to slip into your pocket. But if you have a little space in your rucksack or handbag, it should be fine. It comes with batteries that should be sufficient for 100 prints when fully charged.
So, is it any good?
The prints are of decent quality, but not incredible; if you develop your photos or use a development service in Boots or a similar option, chances are they'll be better. This though is instant and works in the moment you want it, not when you next have time to go to the shops. The key thing to remember is that the pictures it prints are the size of a business card, so these are more throwaway fun prints than the kind you'll want to frame and keep forever.
The app (I use Android devices, so can't try out the iOS version) is fine and works well, so if this is the sort of thing you think would work for a future event, I'd say grab one.
I deducted one star primarily because I think something like this should be just under £100, really, to be good value, given its functionality. Additionally, I would have loved to add this to Google Cloud Print as a printer (which would mean I could send files to it from many apps in the latest version of Android) but don't think it can be done.