The radio triggers are properly handled or packaged and provide 2 key features that are otherwise only for significantly more money:
1. ETTL II (flash intensity is automatically adjusted by the camera)
2. High-speed sync (flashes with very short times, as one example, needed as fill-in flash in bright conditions).
Of course you can first buy cheap Funkauslöser without these two functions and then upgrade. However, the price differences are so small that you pay actually has 2x and what are back in the closet.
With a Canon 5D Mark II the Yongnuo work right away and properly. In the Camera menu, I can select anything. With 2 buttons on the sides I can also quickly change the radio channels and flash groups. A clean on good paper printed manual in English is. But you do not really need. In the receiver, a genuine Canon Speedlite 430 EX II. Worked just sat perfectly. False alarms, I have not noticed. The advantage is the remote trigger can work without changing both the transmitter and the receiver. 2 AA batteries (per Funkauslöser) everyone has to operate at home or as a substitute while traveling. No lithium cells or something, what one then gets difficult abroad especially.
Who wants to play it safe, with a German trader, the Yongnuo Funkauslöser best buy Amazon shipped. It depends a zero duty rate of China and complaints and warranty run for a few euros more from problems. So I did it. Alternative is Hähnel Tuff TTL wireless flash trigger set for Canon DSLR and Speedlight flash units 2.4GHz at a similar price.