Definitely possible, though you would store those tweakable variables in special MyVariable objects (rather than have them be normal C++ variables). With Circa you could grab the object that holds then variable's data, and then have C++ code that reads it as often as you want.
Game devs love to have tweakable variables, so there's a lot of libraries that will help with this. One example: http://www.antisphere.com/Wiki/tools:anttweakbar