Messaging app lets you leave secrets on street corners

Find the right spot at the right time, then burst the bubble (Image: Ljudmilla Socci)

It's your birthday and a message from a friend suggests you go to a nearby street corner. There, you hold up your smartphone and see a water droplet hovering in mid-air. You align an on-screen target with the droplet, bursting it to reveal details of a birthday surprise: a video clip of Arcade Fire's next single, say, plus e-tickets for their gig at the venue across the street.

It's a strange way to give someone a present, but the immersive messaging app that makes it happen, Traces, has just hit Apple's app store.

The team behind it believe that linking content-stuffed messages to a physical GPS location, and using augmented reality Movie Camera

to make it seem tangible, will add real-world context to social media.

"Facebook and WhatsApp broadcast frequent, out-of-context information that's of very little value to you, leaving you a completely passive receiver," says Beau Lotto, CEO of Ripple Inc, based in San Francisco, which created Traces.

With Traces, the sender creates a digital "payload" – any combination of text, music, images, video, tickets and vouchers – and sends it to their chosen person. The twist is that the receiver can only unlock the message if they are in the right GPS location at the right time.

To send a trace, the sender simply selects a person from their contact list, drops a pin in the map where they want it to be visible – and for how long – and then uploads whatever content they want to leave there. Recipients of a trace get an alert on their phone with a map showing where their message can be collected – and who has sent it.

"Instead of reading tweets in a random location you can choose the location to add context to your delivery," says Lotto.

The app exploits aspects of human psychology that Lotto, also a research neuroscientist at University College London, thinks will make it more engaging than traditional social media. For instance, it avoids mass broadcasting by allowing someone to send traces to no more than five people at a time. "We can't be social with everyone," he says.

Volunteers who tested the app have enjoyed playing around with it, particularly hunting for the trace droplet. It could have a range of uses. For example, you could leave a piece of music for someone in a location meaningful to both of you, like where you first met.

People could set up treasure hunts, or add a soundtrack to their street. Publishers are also looking at how Traces could leave location-relevant author and poetry readings. You could even send yourself a trace in a large car park to remind you where your car is – as you'll see the droplet floating above it.

The app has also potential for sampling or selling music, and Ripple is in advanced talks with a major record label.

"This is an absolutely cracking idea," says Paul Green of Arkessa, an internet-of-things developer in the UK. "I can see it giving people customised, context-rich tours of major museums."