802.11 location tracking has been done before.
by R. Proffitt - 2/13/12 9:34 AM
In Reply to: Best wireless router/access point for position tracking by sckulkarni246
And if you've done your research you should have found that it's fine in a laboratory setup but fails miserably in the real world. One of the biggest problems was reflections and a changing environment.
But the RSSI in your 802.11 Android phone from the API I looked at just a few months ago is a simple 0 to 100 value.
Good luck in your project but be sure not to try to go commercial with this.