It's mobile phone friendly, I just created a bookmark on my phone's main screen and document as I fill up. I'm averaging about 16.3 mpg driving mostly city and idling for long periods of time. When I've had the opportunity to get on a road trip I get more like 21 or 22 mpg.
If you have an iPhone you can also use car minder. I use that to record schedule maintenance as well as gas mileage averaging 16 mpg over past 4 months in my v8 with AT and a roof rack. I consider that good coming from a vehicle that got 10-12 previously, the make rhymes with cheap.