Harken have now launched a new digital rig tension gauge

"Unlike inaccurate spring-loaded gauges, the Harken RigTune Pro measures rig tension to the nearest kilogram. As rigging is deflected over three pins on the back of the gauge, a load cell records the pressure on one of the pins. The measurement is displayed on a simple, easy-to-read screen. The RigTune Pro accommodates a specific range of rigging sizes (2.5-5mm), reducing the need for multiple gauges and eliminating conversion tables"

More details can be found at http://www.harken.com/press/Harken-Rigtune.php.

Retail price is rumoured to be just under £200 though - compared to £34 for the Super Spars gauge or £67.25 for the professional Loos gauge the main question is will it be worth it?