In addition to OSM & Google, it would be great to have the OS maps for the UK as an option. OS publish their maps and have an extension to the openlayers API called OpenSpaces.
If you could give some pointers to how to extend your plugin to include OS maps as an optional layer. I would happily have a go and if successful your welcome to use it in any future version. Although I am not much of a programer to you might need to make significant improvements .
Obviously if you prefer I not hack your code, just let me know.