Long long long time back i had worked on HC-05 module for SPP data transmission. Have a look here.
Didn’t work on them after that. These are good for quick prototyping. You can use them.
Now for Bluetooth applications i recommend TI SensorTag.
Here is a board i designed based on TI sensor tag CC2650.
If you can, use the sensor tag in your applications, It will be a good learning process. Very nice features and BLE is going to be a important part of IOT.