I have loaded a KML file onto an Android device. What's the easiest mechanism for loading an overlay of that KML file into Google Maps? I do not want to upload the KML file to the web but would rather open it locally.
To load kml into Google Maps on Android without writing an app, you can create a little html file somewhere with a geo-uri link to the kml file and then click on that link in any Android web browser.
For example: suppose your kml file is located in /sdcard/overlay.kml then you write a geo-uri link like this:
<html>
<head><title>Example KML link page using a geo-uri</title></head>
<body>
<a href="geo:0,0?q=file:///sdcard/overlay.kml">overlay.kml</a>
</body>
</html>
Clicking on the link will launch Maps and then Maps will attempt to load and your kml.
(Obviously if your kml file is on a web server the file:// part can be replaced with http:// servername)
Be warned however that the Android version of Maps does not appear to handle the same version/range of kml elements as the desktop version (or desktop Google Earth).