You're already likely familiar with using site:superuser.com to limit your query to a single website. For example, typing this into the Google search box limits your search to superuser.com:

reboot site:superuser.com

Now, you can use the OR operator to add another site to your query:

reboot site:superuser.com OR site:android.stackexchange.com

You can try the above searches with these links:

• https://www.google.com/search?q=reboot%20site:superuser.com
• https://www.google.com/search?q=reboot%20site:superuser.com%20OR%20site:android.stackexchange.com

Bookmark the resulting link after changing them to your websites of choice, so you can run other searches later without having to type everything again on your tablet.

It looks like GAPI is using the old Google Search API which has been officially deprecated as of November 1, 2010.

If you want more results you should look into another library or implementing your own using the Google Custom Search API:

https://developers.google.com/custom-search/v1/overview