Awesome idea and seems like a slick implementation. Without reading the tag line, there's definitely going to be confusion with https://www.getharvest.com
Pretty nifty that you can set up a Stripe account directly through them in order to kick off your account. Wondering whether they'll open it up in the future. Ultimately, I dig any tool that helps non-profits help others. Nice idea.
Customer.io
Stark
Retention Factory