I embarked on this same search a few months ago. Unfortunately, I never found something that met all of my requirements. I ended up going with Harvest (http://w

I embarked on this same search a few months ago. Unfortunately, I never found something that met all of my requirements. I ended up going with Harvest (http://www.getharvest.com/ http://www.getharvest.com/). Harvest works well, until you want to do something that they don't specifically account for, or if you want complete control over your data. It does integrate invoice creation nicely, which saves me some time. If you find anything that matches your requirements, please let me know. I've been thinking of writing my own.