I'm still working on our privacy-friendly web analytics tool Pirsch Analytics (pirsch.io) like a madman :) I've been doing this for 3 1/2 years now and I'm still super motivated, especially because it's challenging from a technical point of view, and very rewarding (I live off it now).
There is still a lot to do and learn (especially in the marketing department), but we have plans for a new product in the privacy space. I don't want to say too much about it until we've started working on it, but it's in the compliance space and fits quite well with our existing product. I think it's always a good starting point to solve your own problems.