When my battery died, I bought a new one from Halfords for £110. Car sat for about 2 weeks without being used with the iOBD2 plugged in. Battery was completely dead when I next got in, not even a light on.
The iOBD2 is WiFi as I'm sure you know, so maybe that has something to do with it. If it can kill a brand new powerful battery in a couple of weeks, it must be draining quite a bit of power searching for the phone all the time or something.
I have a Y adaptor fitted to my OBD port so I can have the iOBD2 and throttle controller both plugged in at the same time. Is that an option for you? You could place one port somewhere thats easily accessible so you can easily plug the reader in when you get in?
http://www.amazon.co.uk/OBD-II-Splitter-Extension-Female-Adapter/dp/B00F5T0VHI/ref=sr_1_3?ie=UTF8&qid=1401149368&sr=8-3&keywords=obd+y