I've always wondered about this! It is something I've wanted to do even - not for any particular reason other than it seems like it would be interesting to see what other people around you are texting.
Thank you for sharing this article, to bad it doesn't go into more detail on how one might go about actually doing this - other than the price makes it well not worth it - $1500 ouch. I guess unless you've already got half the equipment and the other materials can be sourced. I assume they could be counting the cost of a computer and a transmitter in that price tag. Receivers and transmitters I don't think are all that hard to make and you might be able to use an old phone.