More and more mobile phones and PDAs have built-in sensors that can detect position, light, and motion. Now researchers at Hewlett-Packard's (HP) Bristol, UK, lab are writing software that lets people have a little fun with these sensors.

Last week, HP Labs launched a site that offers location-based games and city walking tours. The site also offers a tool called a wizard for modifying some of the existing games and tours, and a downloadable software-writing tool kit for more-advanced users who want to create applications from scratch.

"We think this will be a new genre and a new medium of experience," says Phil Stenton, research manager for the project, known as mscapes.

The HP project combines physical data with virtual information, a concept that's known as augmented reality. As location-based technologies have improved and PDAs have become more powerful, various forms of augmented reality have been gaining traction. Nokia is working on a project, for instance, that will help people navigate new areas. The user simply points a cell-phone camera at a restaurant or office building, and, using GPS coordinates, software associates a hyperlink with the image. (See "Hyperlinking Reality via Phones.") In the commercial world, some museums and tour companies--including one that takes people around San Francisco--use location-detecting gadgets to guide sightseers.

HP has been developing its own applications for about five years and recently decided to let others "have a go" at the software, says Stenton. What makes mscapes novel, he says, is that it is giving a large community of people access to the research software and allowing them to create, modify, and share their work with other people.

A simple example of an mscape, says Stenton, would be a guided city walk for out-of-town guests. It would be useful when a friend arrives in town but you have to work, he says. You could create a city tour from the website, download it to your PDA, and hand your friend the gadget so that he can explore on his own. Text, video, or pictures could pop up on the PDA screen as the friend reaches a point of interest. For instance, as your friend passes a local taqueria, the GPS position would trigger a picture of you and your friends eating there, a note about how great the vegetarian burrito is, and instructions for where to walk next. As your friend reaches the next destination, such as a park, concert video from that venue could pop up on the screen. Or you could create an audio-only tour featuring stories that you record, as well as walking directions.