My gym has an station that tracks weight, BMI, Body Fat %, and blood pressure. It only holds 5 readings at a time, but it stores the rest on an accessible website, so I was told by the trainer to do it once a week.
A few other tips he suggested:
- Do the data collection before my workout.
- Do it the same day (and time if possible) every week.
I find my daily readings to sporadic to help me usually on the digital scale at home. Since I'm trying to lose weight on a weekly basis (ie. 2-3 lbs a week), I'd rather not see that yo-yo'ing every day for psychological reasons.