I've tested it on the POSE Palm emulator and on my Handspring Visor. You'll need Sun's KVM package to run it.
Instructions Use the radio buttons at the bottom of the applet to select the curve-point mode.
In add mode, clicking on the display will add a curve control point. In delete mode, when you click on a control point, it will be removed. In move mode, you can click and drag control points. Select the curve type from the radio buttons on the top of the applet. The clear button will remove all the control points.