The winning entries in Google's Develop for Good hackathon have been announced and are on show.

If you are contemplating entering one of the many developer contests that we alert you to from time to time, you might be wondering "What is the strength of the competition?", or "How polished should my submission be?" And even if  you are not inclined to enter a competition at the moment it's still interesting to see what other devs can achieve in response to a challenge.

In conjunction with the Extended Events for I/O 2012, Google announced a hackathon in which teams were invited to enter submissions that would "improve the world" in one of three topic areas, covering political and environmental issues.

The contest was announced on June 14 and the deadline was June 29, allowing barely 2 weeks for submissions.

After more than two months the judges made their selections and announced the winners in each category, providing links to each of the submission websites where you can learn about the teams and their ideas:

• Google Ideas: Conflict reporting for blackout situations in repressive regimes

was won by a team from San Francisco with a product concept for Silent Lens; an Android application which would allow citizens to safely send encrypted image-based messages over multi-modal ad-hoc mesh networks. The app would allow citizens to anonymously report issues or violence in repressive regimes when other phone or Internet connections may be temporarily limited, or intermittently severed.

• Google Politics & Elections: Citizen Engagement for Politics & Elections

was won by  a team from the Lagos, Nigeria for a prototype for Assembly Bills; a web based platform that can help Nigerian citizens provide input on legislative bills and policy remotely, without having to fly across the country to the capital of Lagos to provide input in person, as is currently necessary.

• Google Green: Help us all be a little bit greener!

was won by a team based in Karachi, Pakistan with Green it, a Google+ based app that would allow users to report local environmental concerns, gain validation of the issue via nearby smartphone users and aggregate reports in a public online interface. Users would be encouraged to participate through a rewards system.

The winning teams each received tickets to attend I/O 2013, along with the honorary title of "Google Developer for Good, 2012".