Creating Custom Speed Alert POI

Forgive me if this has been asked and answered many times before. Perhaps a moderator could move it to the right place.

I want to create a POI that will alert me when I reach a certain speed. For example: I set it flash an image and emit a sound (wav file) whenever I reach 80mph. I thought I could use my home as a proximity point. Can I set the proximity several hundred miles away ? So wherever I am it will alert me if I cross the 80 mph mark. If proximity points are limited by distance, then I could set several of them spaced apart to cover my travel areas.

I have the POI loader from Garmin but have not used it yet. Any advice, hints, tips, or even telling me exactly how to do this would be great.

Thanks !!