ATTiny85 and USB with Android?

I've been working on developing an Android application that will act as a host to an Arduino based Digispark development board. One of the problems with the board is that it doesn't have a dedicated USB controller, instead it uses a software implementation of the low speed USB bus.

The most generic and best way to communicate data between an ATmega microcontroller and an Android device, without having to rely on special drivers, or having to use special tricks as rooting the device?
There is a commercial library called Slick USB library, but it costs 100 USD, which is way too much.
I would like to use ATmega, MAX232, and USB-to-Serial adapter based on FTDI chip, to connect to the Android smart phone or Android tablet device.
All I want to do is send/receive serial data to the Android device, and process/parse it from within HTML5 application. No native Android application if possible.
Any help is appreciated.
Note that cost is important issue, so no commercial libraries or expensive USB bridges can be used.
Neither any rooting of the device.
We want to use this on several tablet devices in the feature, so cost is important.

Hi....I already found that.And seems that host is possible. But the question is if it's android works with low speed.
About dedicated usb host controller. Normaly they are big. And to check just one voltage line the Attiny85 just works.