I have looked all over the place for one of these. Let me know if you find someone in Europe shipping it for a decent price.
Yes, this little thing really will fix your flat. Even huge pick-up and SUV tires. No need to jack up. Just press the nozzle -- whizzzz -- and it repairs and re-inflates your tire. You definitely should carry one in your car or truck. At $5 it is cheaper than getting your tire repaired at a shop.
But that's not the best thing it offers. This amazing can of stuff will also PREVENT flats and slow leaks. Fix-A-Flat inserts a complex liquid into your tire. Leaking air instantly polymerizes it to plug up any hole. This magic material is similar to the stuff which keeps bicycle tires intact -- see the amazing video in this review. Although I have not used the industrial version of this invention, farmers and the army use a similar compound to keep their gigantic tires going.