Use Amtech installed onto 25 laptops, 1 for each sparky, downloading to memory sticks for merging onto my main database. very easy to use and saves huge amounts of time for me. Have used NICEIC own system and that was a bit more of struggle. Dont know about any others though so might be something better out there.I know some test instruments (Megger,Fluke) come with a package for downloading results straight into a cert but have never used one so could not comment on if they are any good.
Only annoying thing is that we used to pay for NIC certs to print onto but have since educated clients that Amtechs own certs are fine as long as our reg number is on them they dont have to be the red certs clients are all used to seeing from NICEIC approved contractors.
If you do domestic work mainly the basic Amtech package will sufffice but if you tend to do more industrial/commercial installation work then I would recommend getting PRO Design system as well, it is pricey but is a handy bit of kit.
Hope this helps