Great article from S.Jespers "The HTML5 Flash Marriage: Geolocation"
I wrote quickly a simple class you can use to insert a google map with html5 geolocation.
gps(width:int, height:int, APIkey:String, getGeoFunction:String, sendGeoFunction:String)
ie : var map:Sprite = new gps(950, 400, "YOUR API KEY HERE", "getGEO", "passGEOToSWF");
Sample page : geoSample.html
You can download the project : http:www.dipi-graphics.com/download/gpsAs3Project.zip (FlashBuilder Project)