Hey mate!
You need microcontroller to interface with bluetooth. Bluetooth is basicly serial communication, only wireless (simplified explanation).
Also you need to interface microcontroller with multimeter, basic sequence how I'd do it;
init bluetooth->gather data to be sent via BT->send data.
But, before going further, what receiver you have, and what transmitter, as we need to deal with pairing too.
(example of receiver-transmitter pair would be pc-dongle and say hc-05, or hc-06, only latter can't serve as master, IE it can't pair, or like can't queue pairing, it is only paired to master IIRC)