With 1 million users and engagement five times higher than its closest rival, Banjo appears to be the app to beat in the emerging social discovery category.

The service, which allows users to see location information, geotagged updates and check-ins shared on Twitter, Facebook, Foursquare and Instagram, took nine months to reach the 1 million member milestone.  However, what is most impressive about Banjo isn’t how quickly users are trying the service, but how sticky its proving to be.

Although Banjo doesn’t provide exact useage figures on a regular basis, at the beginning of the month the service reported it had just over half a million monthly active users and 900,000 total members. According to Banjo’s founder and CEO Damien Patton, Facebook and Twitter are the social networks users most commonly add to their Banjo accounts. While logging into Facebook is optional, looking at the number of members who choose to use Facebook Connect can provide an estimate of Banjo’s growth and retention.

According to our traffic tracking service AppData, Banjo currently has 290,000 monthly active users and 250,000 daily active users logging in through Facebook, giving the service an incredible 86.2 percent engagement rate. If about half of Banjo’s MAU are logging in with Facebook Connect — high for a mobile app, but not unlikely, given the nature of the Banjo’s service — it means almost all of Banjo’s active users log into the app every day. When we asked Patton about Banjo’s retention he declined to provide specifics, only saying his app’s “active user rate and engagement rate is extremely high.”

By comparison, Banjo’s clostest competitors Highlight and Glancee (both of which prompt users to log into Facebook on the launch screens of the app) post retention rates five to 10 times lower. According to AppData, Highlight currently has 60,000 MAU, 4,000 DAU and an engagement rate of 6.6 percent. Glancee shows 20,000 MAU, 3,000 DAU and a 15 percent engagement rate.

Patton credits Banjo’s success to the fact that the service can be used in many different ways. Users can log into the service to check up on their friends and see the content they’ve been sharing, but one of the most popular use-cases for the app is virtual travel. “During Carnival in Rio we saw a tremendous amount of people from all over the world come in to Banjo and look at what was going on there,” he explains. “People were using the service to look at the pictures shared from Instagram and see what people were tweeting about.”

The majority of Banjo users are in the U.S., but the app is also extremely popular in Spain, Italy and Turkey; Patton tells us the Banjo team is working hard to make the app appeal to users all over the world. Banjo is currently available in six languages, but support for more languages and international social networks is coming soon. Patton did not reveal which social networks Banjo would support next, but did tell us the most requested services were Vkontakte, Sina Weibo, Renren, Mixi and High5. Banjo is backed by BlueRun Ventures and Lightspeed Venture Partners.