Use the left button to turn the redstone line off, the right button to turn it on.
Dig a one block deep hole, put a redstone pipe through it, and build a NON sticky piston on the left and right, the one must be one block away. On one side of the redstone line build a permanent source, like a redstone flare or redstone block. Now just build a block between the pistons and connect them.
Can be used well for alarm systems and lighting.