I guess it depends on what you want it to do – I use MapMyTracks – on my LG KC910 Renoir – seems to work well for what I want to use it for – but then I don't want to see myself on a map whilst riding. It does do real-time updating but that requires a signal on the phone so it can update it's site every 60 seconds (I think). If you don't track online in realtime then it just stores your ride and once you stop tracking asks if you want to synch it online – in which case it adds it to your profile.
So if you want a GPS tracker for just noting where you went then that works, but if you want one that will give you maps and stuff of where you are at you need something a bit fancier (the iPhone version of MapMyTracks – OutFront – does mapping and stuff in realtime (but relies on a phone signal as well)) but this will also have a drain on the battery.
I'm still experimenting with my phone location on me whilst riding – if there are no trees it seems to work well in my knee pocket – with trees I think the phone needs to be up near my head and on my back i.e. pocket of backpack.