Anything that could be verified via picture can probably be achieved by tweeting a picture and tracking with a Twitter integration. If you’re tempted to bank on anonymity and tweet unrelated or false data, let people in your life (or this forum) know what the account is and invite them to randomly check that everything is legit.
Other sorts of goals would take a bit more creativity. In general, your goal could be to set things up so that it takes nearly as much effort to falsify data as it does to just do whatever the activity is. That can be achieved either by making it really difficult to lie, or by making the goal really easy, as with the “floss one tooth” sort of tiny habits.
When I was breaking my weaseling habit, I had a lot of success with Beeminding my weaseling. It gave me just the mental wiggle room I needed - I could weasel on a goal, but was it really worth burning up whatever weaseling-buffer I’d developed (and possibly derailing that graph)? This of course requires you not to weasel on your weaseling graph - it might be a good idea to cap the pledge at a low value (or even $0), so that you’re not ever tempted to lie. If you can make that a firm line, it might be an effective technique for you.