Four point harnesses are for non-competion purposes. Schroth makes DOT legal four point harnesses that can be used for street use and high performance drivers education events (track days etc.). I suggest the Ralleye or Quick Fit models for BMWs.
http://www.schrothracing.com/tuning
http://www.hmsmotorsport.com/store/schroth-tuning-belts
http://www.modernperformance.com/pro...gauges_schroth