itunes.apple.com/us/app/lamp-words-for-life/id551215116?mt=8
I have no idea how it compares to the Vantage Lite (which DS1 uses for LAMP) but the screen shots look very similar. DS1 didn't get on at all with Proloquo2go but has done amazingly well with LAMP. For example this morning he told me that he wants the CD that is in the car to be played in the kitchen. And he told me that next week he isn't going to school in my car and he isn't seeing our direct payment worker but he's going to school. And in October his grandparents are visiting and staying in a hotel. And so on and so forth.
This level of communication was utterly unavailable to him prior to LAMP. I have a link to my blog on my profile if anyone wants to see LAMP in use (there are some videos) but definitely worth checking out the app as well if you're interested. It's still not cheap - but it's a lot cheaper than the Vantage Lite. Incidentally I suspect the programming etc required for LAMP might be more complicated than that of category based AAC systems which is probably why it's more expensive than some other systems.
LAMP UK who run workshops which I think might be free (??? not sure ???)