There is an aftermarket kit available for Recaro seats (which the Porsche basic seats are). AutoSport Engineering in Stow, MA showed me this when I was there for a service visit and they were going to check to see whether the solution would work for stock Boxster seats... I got distracted and never called them later to find out whether they were able to make the fitment work. It was supposed to be well under $100 (per seat, installed).
The blood pressure cuff idea is interesting. How well does the cuff fit, how did you fold or otherwise prepare it? How far does it come up the back of the seat? Did you keep the pressure indicator for the "tech look"?
