One of the BMW approved tie downs and bringing a car onto a flat bed is the use of
T hooks.

Been buying these for some time.
What got me to buy them now was an emissions OBDII check and a recent friends accident. I talked with three local towing companies in CT and none were aware of the BMW T hook capability.

Found a nice place to do the emissions check this summer. My 318ti went through with no problems. When I brought in the coupe a few weeks ago they couldn't connect via the OBDII port. My OBDII software and the emission check places scanner did. The AGBAR emissions company equipment wouldn't. They have a new name now based on the law suits which I don't remember. Turns out other states VA, PA and one other that I forgot can't hook up either. I assume it's the same company.
Well as of now the emissions place or you have to call DMV and they send out a guy (another visit). The DMV guy never returned the calls (two days). I called and he called me back with an appointment for the third day. I assumed he was going to get around the software some way. All he does is approve a tail pipe test. By December they say the software will be modified to automatically switch to a tail pipe test if they can't connect.
We pay them millions to do the emissions check and they still haven't figured it out yet.
Well if they do a tail pipe test they have to tie down the car which the emissions place is not capable of doing using a BMW recommended way.
Another advantage of the OBDII check is that if you have the OBDII software you can check ahead of time whether it will pass or not. You can see if the readiness bit is set or not. You don't have that option with the tail pipe test.
To use the T hooks you have to remove the jack pads under the car. Behind each front wheel and in front of each rear wheel. Earlier Z3's snap out. My '01 pads are held in place with two Philips head screws (from 8/97).

I purchased mine from AWDirect in Berlin, CT. They specialize in towing related stuff.

http://www.awdirect.com/

They sell the same ones that others sell for more than twice as much. They also sell some nice gas cans. One of them is the same one Griots sells, but less.
They have a walk in factory store. Anything ordered via internet before 5 PM eastern ships the same day. I had to pay 6% sales tax but they discounted 5% on my order.

Will reserve some posts for further info on towing, tie down, battery jump and roadside assistance.