Activate geolocation on homepage, google addresses as backup

On the homepage of my website i want to enable geolocation. Alternatively if the user does not want to use geolocation he must be able to provide a start point by entering an address using google's auto-complete. Alternatively to that he must be allowed to set a startpoint by clicking on a map. Either way i need a startpoint, in the form of global javascript variables, that i can use in location related searches. If the user refuses all 3 methods then the searches just don't work, his loss. I need this in a Joomla module however if i have the bare PHP/Javascript code i think i can incorporate it in a module myself. Primary requirement is that you know how the google maps API works !