These systems are a "great idea" for the masses of drivers that don't pay enough attention to check their own tire pressures (i.e. not like car enthusiasts that read forums like this one) or to know when they have a flat tire. I can't count how many idiots I see every day driving around with one or more tires that are 10-20 psi low... especially the first day after the weather changes from warm to cold.
These tire pressure systems have downsides, especially the ones that measure pressure directly inside the wheels (the only ones that really measure tire pressure, not relative wheel speed interpolations). There are wireless pressure transducers mounted to the rim and/or valve stem that are 1) heavy, 2) fragile, and 3) expensive to replace. Its easy to mix up their location (tire rotations), and tire stores charge a premium to swap tires on rims equipped with them (because its very easy to break them).
On cars where the OEM wheels have been removed/changed, there are rumors of some models that if the signals are missing the ECM notices and thinks you are on 4 flat tires, and limits engine parameters. This is a rumor only, and not applicable to all cars. I've personally owned 2 cars with these systems ('05 Corvette Z51 and '05 RX8) that were used with aftermarket wheels/R compound tires, and it just turned a light on the dash and didn't hurt performance.
Something to think about tho. If its optional, don't get them. If they come with the factory wheels, well, great. Just replace those wheels when you can. :biggrin: Most BMWs come with skinny front tires, and Run-Crap model tires anyway - which are the worst tires ever made for performance enthusiasts. Again, they are for the cluless masses that are too stupid to know when they get a flat and too lazy to change to a spare when they do.
Not like people here.