The public Gowalla API was first announced in February. Devs built apps such as Users Like Me (it is what it sounds like) and GowallaWalk, which shows a simple map of a user's checkins. While these apps could gather and compare all kinds of interesting data, they weren't really interactive with Gowalla itself.
What today's release adds is the ability to check in via a third-party application using OAuth 2.0.
Foursquare's API (checkins included) has been live since last fall and has sprouted many interesting mobile applications, from social games to shopping/discount apps and far beyond. At that time, we wrote, "The API release is one of the most important pieces to the company living up to its potential... because it allows developers to make location and places relevant."
In the past six months, many Foursquare-based apps have popped up on our collective radar; still, location-based service adoption remains a badge (pardon the pun) of the tech elite and few others.
So far, only 4% of the adult population of Internet users has ever signed up for a location-based service, and only around 1% use LBSes on a regular basis (at least one checkin a week).
We hope that the availability of more useful APIs will encourage creative uses of location-based apps such as Gowalla and hopefully prompt a steeper adoption curve. If you're interested in learning more, check out Gowalla's checkin API documentation and guidelines.
What kinds of games or other applications do you think could help LBSes as a group and Gowalla in particular blow up for a mainstream audience?