By the way, a mode s generated radar picture can be streamed over the internet and in fact you can get that for the area around Schiphol via this website:
http://www.atcbox.com/modules.php?na...bs1-live-radar
I have no idea if that is legal in the netherlands so use it at your own risk.
Back on the Mode S issue: at the moment every aircraft that uses ACAS II has to use a Mode S transponder since ACAS II requires the mode s datalink feature for its coordinated RAs. But additionaly to that every aircraft has to be equipped with Mode S from a certain point on (i think 2008 is correct for small aircrafts), airliners have to be equipped with Mode S Advanced Surveillance (vs, Elementary Surveillance required for small aircraft and required for TCAS now) from 2007 on, with that you can see a whole lot more information and the idea is to get an ADS-B like picture with that information alone.
Quite a lot of information will be transmitted with those advanced transponders, namely callsign (have to enter it correctly), magnetic heading, indicated airspeed (no cheating anymore), Mach No, selected altitude, barometric rate of climb/descend, roll angle, track angle rate, ground speed, true track angle, position etc. It is expected that all of that information will be used with ground based atc anti collision software and some if not all of that will be displayed to controllers if they wish so. Most newer commercial aircraft are allready equipped with a transponder complying with that profile so you will see quite a lot if you chose to use something like the SBS 1.