This is a much needed service! At Standard Treasury we set up a 401k (no matching, we're a poor startup) through Zenefits, which ended up connecting with https://www.myubiquity.com/ (formerly theonline401k.com). Ubiquity has an unpleasant and unintuitive user interface, poor support, etc. I'm really glad to see a YC company taking on this space, it's worthy of attack.