I'm in the same boat right now in looking at different modes for tilt/nudge on my HyperPin build. We have a couple threads on the HyperPin forums regarding this. Below are several that have been discussed:
1. Wii remote via Bluetooth and Glovepie script. The accelerometer in the Wii mote would feed info to the PC in regards to the bump/tilt action.
2. Ultimarc UHID-G. This too is an accelerometer that detects motion and subtle bumps. I already have one of these and will be testing it shortly.
3. Tilt buttons - basically just extra buttons on each side and front of the cab. Press button = bump/nudge.
4. Tilt bobs and slam switch from a real pinball cabinet. These would be tied into my keyboard encoder that hooks to the PC and interfaces all of the controls. The tilt bobs would be taped off one one side so it doesn't make contact when the opposite direction is bumped.
5. Nudging lockdown bar - This really seems like one of the best solutions. The lockdown bar is the bar at the front of a pinball cabinet that locks the glass into place. One of the HyperSpin site members drew this up and it looks like it would work quite well. I'm thinking about trying this, but I have no welding skills and I'm wondering if JBWeld would hold well enough for something like this.
6. NanoTech Mot-ION - This is probably the most expensive way to go. Unfortunately the reviews of the product have been less than stellar.
As far as my pinball plunger goes... I'm going to have both a real pinball plunger and also a launch ball button. My pinball plunger is configured using a custom optical switch.
BTW - If you are not a member yet; you should join the HyperSpin-fe.com site for our HyperPin section. This is one of the best resources online now when it comes to digital pinball builds.