Button does work with the type of apps that run on your phone. It connects them to each other, for example so people looking for restaurants on Foursquare can call an Uber within the Foursquare app. It’s interesting because it gives a direct connection between the apps without the usual detour through the underlying platform to get from one to the other. I suspect the technical challenges are mind-boggling but from a marketing standpoint what matters is a seamless customer experience based on ever-closer connections (and data sharing!) among customer-facing systems. Button just raised $20 million, bringing total funding to more than $36.5 million.