Any ideas how to solve this problem?

I developing a system that consist of 2 units; 1 Android tablet and 1 iPhone. My users will have to identify themselfs to the Android tablet (this should be done as user-friendly as possible with as few steps as possible and in a secure manner, meaning it should not rely on gps that is not exact). I have looked at various techniques, but each and everyone of them seems to be inpossible to do:

idea #1: The iphone app has a barcode. The Androi开发者_运维知识库d tablet scans the barcode using zxing (with the built in webcamera). This seems like the best idea but I cant get a hold of an Android tablet with a camera good enough to run zxing.

Anyone that knows of an Android tablet that can run Zxing or does anyone know of any other api that I can try (except shopsavvy).

idea 2#: Using the bump api. This doesn't seems lika a reliable method since 2 people next to eachother can bump 2 seperate Android tablets. Any input on bump?

idea 3#: Using bluetooth. Letting the Android tablet connect to the closest iphone (locating it on RSSI). The problem is that iPhone doesnt allow Bluetooth connections!?

idea 4# Using NFC. The problem is that iPhone doesnt support NFC.

idea 5# Using P2P wifi. As far as I know this seems like a challing thing to develop (finding the cloesest found etc.)

Anyone that has another take on things?

Uhm... would it be possible to create a mobile website that allows users to first register their tablet, and then provide some kind of key that the iphone users can use to log into that site as well? Depending on what you might want to do subsequently with the connected machines, serving something on a website might be the easiest.