On the Garmin 660 it is easy to add thousands of poi to an sd card and import into the Garmin.
I have worked on a spread sheet that imports the route i am taking on a trip like from Chattanooga to Atlanta .
I use to bring in all the points i want to be alerted to on my trip. Within a ten mile radius of my route and then download the address into the spreadsheet. The computer converts the address into the corresponding lat and longitude coordinates which i transfer to the sd card. And then plug into my 660. I also add mp3 voice to certain points so my voice or music alerts me . I have my gps recording play lets get a big Mac when i am within 300 yards of a McDonalds.. Enjoy Sam