Drip looks great! I've been using Ovuview which says it keeps your data private, but being proprietary I can't easily know for sure. I love Ovuview for its depth of tracking (Symptothermal plus any custom symptoms you want) and it's accurate predictions.

But will be really nice if Drip works out well (gonna try it for a while first before ditching Ovuview) so I can finally use something FOSS.