Can I connect GPS module (NEO-6m) to bluetooth module HC-05 directly?
UART usually works in two voltage levels. In simple terms, 3.3V and 5V. You will need to find voltage level of the UART used in your GPS device and then match it with the Bluetooth module. If you are unable to do this, you can use level converter. These can be easily purchased through eBay. The most important thins is to know the voltage levels you are operating so you wont burn your GPS.