Hello world Bluetooth hardware
Use a microcontroller with a Bluetooth module.
In theory, you could use a microcontroller and an antenna along with the communications circuitry, but it will be more expensive and power-hungry than using a Microcontroller with a Bluetooth module. Not to mention the time to develop Bluetooth from scratch.
Why would developing custom Bluetooth be more expensive?
The Large Scale Integration of multiple functions on a single chip, coupled with economies of scale will make a microcontroller with Bluetooth integrated (or a discrete Bluetooth module) much cheaper than building Bluetooth transmission using a microcontroller, antenna and discrete components.
Why would it be more power hungry?
Integrated circuits with an integrated antenna have lesser area and dissipate less power compared to discrete components.