I can do with or without it. I actually used it for a long while and just stopped as it's another button to push when you get in. I don't miss it so I never bothered with it again. I am also leery of it getting me stuck as early on in the E70s lifecycle a lot of people were getting parking brake malfunction and having to pull the cable with the tool. But the best use is probably while in heavy traffic and hardly moving. If you need to inch up every few seconds, it's not worth it.

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr