If when they say wireless they actually mean optical (like the Nikon CLS) then you will need some sort of optical trigger generated by the camera to cause the flash to work. That signal no matter how weak may still affect what you are trying to shoot otherwise it would be so weak that in anything but very dull light the sensor on the flash would not pick it up.
I can't imagine it being wireless in the sense that a mobile phone is wireless because there would have to be some sort of wireless receiver built into the flash unit and surely it there was everybody would know about it by now.
You are probably going to need some sort of third party wireless set up to be truly wireless. If manual settings are okay they aren't expensive. You could start by looking at this page