Were you going to use Serial for the BT, or keep it as debug?
If not, be sure to save pins 8 & 9 for AltSoftSerial. It's much more efficient than SoftwareSerial, but it prevents PWM on pin 10. If you need that PWM pin, use NeoSWSerial instead of SoftwareSerial on any two pins. NeoSWSerial is not as good as AltSoftSerial, but it is much better than SoftwareSerial.
I'd also suggest taking a look at my GPS library, NeoGPS. It is smaller and faster than all other libraries, and it can be configured to parse just the messages and fields you actually use. The Arduino in the small box would be using the Adafruit GPS module, not the phone, right?
Cheers,
/dev