By making use of the two low cost development boards below:
(A) CH340 USB TTL Serial Adapter for Arduino like FTDI CP2102 PL2303 approximate cost £2.99
(B) HC-05 6 Pin Wireless Bluetooth RF Transceiver Module Serial For Arduino approximate cost £2.50
A simple bluetooth serial convertor can be constructed.
To assemble the interface, we can either directly connect the two modules together with the cable loom supplied with the USB to serial adaptor or by constructing a linking board from prototyping PCB.
Whichever way is chosen the two modules should be connected together in the following manner: