OK, so you have added another requirement. Not only you must not have to ask for permission, you also must target 90% of the users.

We are in somewhat of a conundrum now, because 90% of the users don't really know how to deal with webapps in a mobile browser, they only understand native apps or simple webpages. Also most webapps suck horribly on 90% of the phones in the world, because their bloated JavaScript requires performance-minded development and high-end phones in order to work.