OBD2 Splitters?

[shovenose]

I want to hide my T-Mobile SyncUp Drive under the dash of my Escape. I'm thinking I can use one of those y cables from Amazon, and putting the second part of the Y where the original OBD2 port was, so scantools can still be connected (smog, diagnostics, etc) but anybody who steals the car won't notice the device, but I'm curious if that actually works. How can two devices be on the OBD2 bus at the same time?

 

[Blckshdw]

I was looking at going this route years go, after I had bought a Scangauge II, and wanted to try Torque with a bluetooth OBDII adapter.

What I ended up doing was grabbing an OBDII plug out of a junked vehicle, with a few inches of wiring still attached. Pulled the knee bolster panel off my TB, and spliced it into the same few wires in the stock harness.

Plugged the Scangauge into the secondary port which was hidden, and ran the bluetooth adapter off the original one. Both worked great for reading different data at the same time, and it only cost me a few bucks and the time it took to splice and tape up a couple wires.