Got the BBQ thermometers a couple days ago. They look just like the one pictured in my earlier post about them.
Reading through the tiny instruction page there is no way listed to turn off the auto shut-off feature. So it doesn't seem to be an option after all. Also the instructions say 10 minutes instead of 15 on their Ebay page. Oh well, I expected that.
I can either wire into the on/off button with a momentary switch on the handle bars (most likely). Or find a way to disable or extend the time on. If it uses a resistor to set the time it might be easy to change.
They were very easy to take apart. There is an end cap that unscrews to access the battery, and the other end with the probe also unscrews. Although the probe end had a drop of glue holding it on it was quite easy to undo.
Now I can install the sensor in the front hub and finish the wiring.