You can't run apps though the touchscreen. All you can do is stream music via bluetooth, use the hands free phone, or if you plug it in to the USB socket, you can select it in the Media source (it shows up as iPod) in order to play music. If your phone has tethering and you have plenty of time to waste, you can v e r y s l o w l y browse the web (while stationary and engine off...) if you set the preferences.
If you want to run apps, you have to buy the Citroen Multiconnect dongle.