Out of curiosity, did you consider skipping the signup requirement/process? Instead, just having a user put in their e-mail address as the only step?

Then it might work like this: 1) user enters email 2) you send daily "What have you done" emails to that address, they reply (which you can uniquely key to your database/calendar) 3) you email out the intended results, or if at a later time a user wants to log into the site to see a fancy calendar/history/graphs/charts, etc., at that time they could complete the signup process

I wouldn't say the signup is prohibitive in any way, and I admittedly did not investigate what features are part of being logged into the site - just a thought as less burden on signups seems to be a growing trend.