Researchers at Stanford University found that people who received automated exercise reminders by phone were as likely to go to the gym as people who had real life trainers harassing them. Keep yourself honest by registering for prodding e-mails from hassleme.com.uk. Plug in your e-mail address, how often you want to be nudged, and a direct order ("Get to the GYM! Now! Love, your incredibly Skimpy Bikini") you get the picture. You can create your own reminders.
Anything helps at this time of the year.