[realtarget]

Well, it's not successful right now but it could be in some months:

Two years ago i've started working on an algorithm to find the perfect time for social media posts on facebook & twitter to improve user interactions & engangement. Right now it works so good for me that i've decided to extend the project by building an (invitation-only) SaaS Startup to get a proof of concept: https://realtarget.com

Because it's just a project beside my main job my girlfriend (project manager) and best friend (senior full stack developer) support me to lighten the workload.

If you like, i'll post a note on HN when the alpha version is ready.