Agree with Cobra about MyFlightBook. Don't forget that you must enter Engine Time Start (by tappping on that field) for the app to know it's supposed to be tracking the flight and automatically be filling in other fields.
Also a separate note on what he said regarding using Tach Time: I use Engine Time (start to end) as my logged flight time, and MyFlightBook will correctly calculate that in hours-&-tenths and automatically enter it as your PIC and Total Time if you ask it to. Per the FAA, flight time "commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing." In my book (literally) that's from when I start the engine to when I turn off the engine. (OK, granted, there's a few minutes in there between engine start and first movement.) But as many of us have been taught: when that prop is turning you're flying the plane. So, I still consider it all valid time to log, even if there's a few extra minutes in there. (Actually, there should be no difference between using (real) Hobbs Time, or (adjusted) tach time, or Engine Time. Sometimes there's a little difference due to rounding. But note that any of those is going to be greater than Flight Time recorded by the app, which is when it calculates that you've lifted off until it calculates that you've touched down. If you use Flight Time as your logged time, then you're shortchanging your hours.)
Jeff: it's an app that runs on Android or iOS, but he also has a website interface. So, if you fly with your tablet and run MyFlightBook on it (and remember to fill in Engine Time Start) then you don't need to enter stuff manually, other than comments and things Cobra mentioned. On the desktop, you can use the website at www.myflightbook.com, which is what I usually use once I get home (to add comments, or look at flight data).