The problem with using '168 or '328 uCs with BT and XBee at the same time is
that there is only one uart. You would need to multiplex that UART between the
two serial devices (or setup digital pins as a serial input). The problem with
the mux is that while you are communicating with one device you are missing
any communication with the other. This may work for your application but not
for most applications.
I would use a board based on a device with more than one UART.
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