AFAIK, capactive touch screens are permisable from a Jewish law standpoint. For example [1] which is a phone for use on shabbat and uses capactive buttons to avoid closing a circuit.
It really depends on your definition of the 39 melakhot. Even the idea of "closing a circuit" being the same thing as "starting or tending a fire" is a modern invention, so some people abide and others don't.
In my opinion if you're closing a circuit you're closing a circuit, and capitative screens count. Others go so far as to disable thermostats since a person's very presence in a room affects the temperature by a few degrees and could trip the circuit. Depends how deep down the rabbit hole you want to go I guess.
[1] http://www.zomet.org.il/eng/?CategoryID=249&ArticleID=99