Not quite sure what you're asking...
ON camera flashes (aka speedlights) sit on the hotshoe, or you can use an off shoe cord (canon's is about $50). You get eTTL, or any other mode the flash offers.
To fire studio lights most will trip if they see another flash - so the on-camera flash can do that, BUT unless you want that flash to add to the exposure you have to aim it away from the subject. If all you want is a flash to trigger with there are alternatives, but any cheap tilt/swivel flash should work. Remember, the studio units have to see the flash go off.
I've had issues in a small studio with studio flashes seeing other flashes so I got Pocket wizards for just about everything now. Not cheap, but the are the best. You can be outside and trigger flashes inside, behind building, trees, etc -1/4 mile away.
There are cheaper wireless triggers but as they get really cheap (like the ebay $20 ones) they get unreliable and trigger when the feel like it. COrdless mice/keyboards, cell phones, flourescent lights can all cause false triggers.
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