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Were you thinking of hooking up a USB Bluetooth dongle for the headset to the USB port on the Garmin Nuvi device?
Or how were you thinking of getting a Bluetooth connection working with the Nuvi?
The Nuvi by itself does have Bluetooth connecting, for hands-free calling, listed among its features, ... but I would need to be sure as to exactly what you were thinking of.
On this device, Smartphone Link does work, with Android or iPhone devices.
(Sorry for the delay in responding.)
How did you try to get those two to work?
And with what result?