Double Up started simply as a self-hosted version of a Slack app called Donut. Like Donut, Double Up's purpose is to connect individuals in a serendipitous way, but as far as I'm aware, that's where the comparison stops. At Test Double, we're a remote company. A remote consulting company, so there is another step removed for some of us as we help different clients from each other.
We needed something that promoted getting together. The requirements were minimal, so we took a stab at doing it ourselves. It was very barebones initially, but it worked. It was set up in a way that used a designated channel as opt-in, so if you joined that channel, you'd be in the list of participants waiting for Double Up to match you. It didn't even have a name at that time either.
For awhile, it worked as expected. Take a certain number of people from a list randomly and then move onto the rest until everyone was in a group. Time revealed that basic randomness wasn't exactly what we wanted, however. We began noticing that some people were in the same group for consecutive weeks. There's nothing exactly wrong with that, conceptually, but we wanted to regularly meet up and connect with a variety of others at Test Double.
Eventually, the app was named Double Up officially and we've been (in short bursts of motivation and capacity) modifying it to better meet our needs and promote connectedness within our organization.