This plugin was developed to embedd google maps into wordpress, it is highly configurable, allows the developer to setup google maps api parameters, also you may define on the widget page the startup position on the map giving initial coordinates, the initial zoom level, etc. The plugin Options allows you setup the api parameters and let you add your own JavaScript code to make your map work. the initialize() functions look if a custom function has been defined, the name of that function is custom_init() you must use it to be able to introduce your own custom initialization code. Then you may add your own functions to place markers, etc.
By Martin > By Martin Maps (WP Plugin)