Haven't seen one of those before but seems like maybe it's used to make getting at the seatbelt more convenient than reaching all the way back over your shoulder.
Edit: Or actually looks more like one of those straps for your luggage where you can strap a laptop bag on top of a rolling bag lol
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SOLD 12/30/2011 2010 370Z Coupe Monterey Blue 6MT/Touring/Sport/Nav
F.I. CBE CF w/ 12" Res | V1 | SecondSkin | Stillen G3 | EVO-R CF B-Pillars | Volk GT-S Ti Gunmetal 19x9.5 +30 F, 19x10.5 +8 R | Swift Spec-R Springs
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