I've tried a few approaches - maybe they'll give you ideas…
For a while I did a regular analsis of my browsing history to show how much time I was wasting… all it took was firefox and a very small bit of excel fu and you could do this sort of thing… (apologies for lack of tabs)
> 01/03/2011 12/03/2011 22/03/2011 27/03/2011
> Youtbue 15 86 41 48
> Facebook 572 1230 454 244
> bbc 82 30 34 63
> iplayer 7 9 4 9
> surfthechannel 0 8 0 24
> wikipedia 171 604 127 220
> TV Tropes 14 29 0 0
> Imdb 2 8 2 0
Also a running total of unread g-reader items is a pretty good clue of how bored I am - this was a quick bit of python that gave out files like this:
2012-01-21 05:00:02 1327122002.99 55
2012-01-22 05:00:02 1327208402.79 50
2012-01-23 05:00:02 1327294802.05 93
2012-01-24 05:00:02 1327381202.94 414
2012-01-25 05:00:03 1327467604.0 739
2012-01-26 05:00:03 1327554003.52 1000
2012-01-27 05:00:03 1327640403.19 886
when I was quite busy and files like
2011-01-03 09:00:02 1294045202.3 0
2011-01-03 09:01:09 1294045269.72 0
2011-01-03 09:10:02 1294045802.8 1
2011-01-03 09:30:02 1294047002.54 2
2011-01-03 09:31:13 1294047073.46 2
2011-01-03 09:50:03 1294048203.02 7
2011-01-03 10:00:01 1294048801.78 1
2011-01-03 10:01:11 1294048871.22 1
2011-01-03 10:30:02 1294050602.09 2
2011-01-03 10:31:16 1294050676.94 2
When I was procrastinating…
I've touched on my productivity graph in other posts - Gamification to improve myself for an example...
and someone is bound to mention http://www.rescuetime.com/ very soon so let's bring that up right away…
Lastly I've been looking a lot at my iPhone's log files for this sort of tracking of things - but even with a jailbreak and a general familiarity with the innards of the device I've not been able to get very far with the debuging logfiles :( you might have a lot more luck with android...