Two or Four x "Smart Finder GPS Tracker" Units, comes complete with CR2032 Lithium Ion Battery each — absolute-magic.com - Find almost anything but the ordinary!
Amazon.com: (2 Pack) CR2032 2032 for BMW Remote Key Fob Battery Replacement Original OEM (Bundle with Remote Opening Tool) for 2004-2011 1 3 5 Series E90 E92 Smart Keyless Remote with FCC ID: KR55WK49147 : Automotive