Glad you asked. I have two features I have on my short list of features I'd like to work on next.
I don't go to sleep at midnight...
As you may have discovered, TrendWeight uses the first weigh-in of each day in its calculations and ignores the rest. I'd like to better support those of you that stay up past midnight and would like to be able to weigh yourself before you go to bed without throwing off the stats. I'll be adding a setting where you can choose an alternative time of day (other than midnight) that TrendWeight will use when deciding which is the first weigh-in of the day. For example, if you routinely stay up until 1 or 2am, you might choose 4am as the start of a new day.
Am I gaining weight because I'm building muscle?
Many have requested support for tracking body fat % in the same way that total body weight can currently be tracked (exponential moving averages, etc). This is a larger project, and will take longer. I am not entirely sure how I'll end up approaching this, but it is on my short list to get done some time this fall.
My initial thought is to allow you to view the stats and charts in terms of total body weight, body fat, or lean mass. This way you'll be able to see if the amount of fat in your body is going up or down regardless of if your lean mass is changing. It remains to be seen how chaotic that data will be. My experience is that the body fat % reported by both the Withings and FitBit scales are significantly less precise than the weights. This may mean the charts are much more erratic unless the data is analyzed differently. Or maybe the charts will be more erratic but still a useful way to gain some insight into what's happening with your body.
I don't have John Walker's guidance to rely on this time (he was the author of The Hacker's Diet and his analysis techniques were the inspiration for TrendWeight). If you have strong feelings about the "right way" to analyze body fat %, total body fat (in lbs/kg), or lean mass (in lbs/kg) over time, please email me at firstname.lastname@example.org.