The diesel DA40 certainly has a fuel flow meter. How accurate it is I haven't found out yet. The figures it gives are pretty fantastic however! 7.9 gal/hr at 100% power! Certainly alot better than our 172 XP, with full power the fuel flow is above 18 gal/hr! Fuel costs a bit more as well.
Totalisers are very useful, but they aren't always 100% accurate. I've used some that have been out completely and others that have even counted the wrong way. Ahh the joys of commercial aviation!