I have a very old and cheap Android tablet that I use for Carly with both Android Bluetooth adapters and the wired adapter. My phones are Android also so that's always an option for me but you might consider pricing a good used tablet just for this use.

I got over seven years out of the original OE BMW battery. They seem pretty good. Hope you get similar service out of your replacement.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim