Cycle computer help?

There may be a total easy answer to this that I am missing, but someone help me.

I have a wired rear wheel cyclometer.  I like the rear wheel setup so I get info when I am on the trainer.  I am planning on getting disc cover for my rear wheel.  I am assuming that the sensor will NOT read thru the cover when I am in a race or riding with with the cover on rear wheel.

What are the remedies for having a cycle computer for "race" day?  Do I buy another computer (wireless) front tire and just swap them out on days when I am riding with the disc cover?  Or are there other options for race day that I am missing?