SIM Access Profile is a Bluetooth profile allowing a GSM phone to share its SIM card with another device of the same type.
This profile allows devices such as car phones with built-in GSM transceivers to connect to a SIM card in a Bluetooth enabled phone, thus the car phone itself doesn't require a separate SIM card and the car external antenna can be used. This profile is sometimes referred to as rSAP (remote-SIM-Access-Profile), though that name does not appear in the profile specification published by the Bluetooth SIG.
Many manufacturers of GSM based mobile phones offer support for SAP/rSAP. It is supported by the Android, Maemo, and MeeGo phone OSs. Neither Apple's iOS nor Microsoft's Windows Phone support rSAP; both use PBAP for Bluetooth cellphone-automobile integration.