Is there a SMS to bluetooth router app? I have a bluetooth device that is paired with my phone.  The BT device can receive and send text.

How can I route incoming SMS text messages to the BT device?  And conversely, how can I have the BT device send an SMS via the phone?
There is no standard for this in the Bluetooth protocol stack, so the solution depends highly on the manufacturer of the device. If the manufacturer hasn't created an app for Android, it's probable that you would have to program it yourself or have someone do it for you. This would require that the manufacturer has public protocol definitions available for the communication between the devices.