I use PocketFMS and wouldn't be without it.
If I had to get a new system, and there was no difference in price, then without doubt, I'd go PocketFMS again rather than a dedicated unit.
PocketFMS software maybe free, but unless you already have an pda, (or work will buy one for you), then it's not going to be all that cheap.
You'll need a PDA, a GPS (bluetooth or card) some sort of mount to hold it, and power it, and a memory card.
dp