I think liquid calcium would work but it would be most effective if administered orally. I have had great success with a liquid vitamin made by Pet Authority called "Leapin' Lizards Electrolytes with Vitamins and Minerals". It can be purchased @ www.reptilesupply.com via the supplement's tab.
If you put liquid calcium (aka calcium gluconate or another substance) the dripper will become a hotbed of bacterial delight. Don't do it. You will drip the equivalent of calcium 'sugar' all over. Bad Bad Bad.
Powdered Ca will not suspend in a liquid well, and frankly it may make the cham look for another water source and stop drinking.
Really. The crickets LIKE to be dusted. It is the height of cricket couture.