Just developed a new plugin. Surveillance now has a plugin for Automatic License Plate Recognition!

It has been tuned for Indian plates and tested with bikes and cars but can be tuned for any type of license plate.
As with any plugin, a wide variety of front-ends to this plugin are possible.  Here is a demo video.
The video and pictures were taken using a mobile phone camera. Results will be even better and faster if your imaging setup has a professional camera and good lighting.
The recognition of the license plate depends on how close the actual font is to the fonts the plugin understands. The output of the plugin as with any plugin in Surveillance is in JSON. It provides the detected license plate in 'description' and the quality of the result in 'long_description'. Your front-end can then decide whether to accept or reject the plate based on this value.
For details about the output Surveillance produces, click the 'For Developers' link. If you know that the cars in your city/country/state use a specific set of fonts, the system training can easily be altered.

 This plugin is presently in alpha stage.