A data transmission module is provided as a battery-less accessory for attachment to portable metrology devices (e.g., handheld digital calipers, micrometers, indicators, etc.). Rather than utilizing battery resources from the metrology devices, the data transmission module utilizes energy harvested wirelessly from a remote data node (e.g., a computer system, display, etc.) to power transmission of measurement data signals to the remote data node. The data transmission module may receive sufficient power when relatively close to the remote data node, such as when a user is near the remote data node when operating the metrology device to obtain dimensional measurements of a workpiece. A wireless data generator of the data transmission module may be configured to wirelessly communicate measurement data signals using: the harvested energy; or a modulated reflection of, or coupling to, a received energy supply field from the remote data node; or a combination thereof.