The invention relates to methods and devices for exchanging control information in mixed radio systems. Security is added in cases where a user of a first wireless device (102) wants to command a second wireless device (101) to perform a certain action. The first and second wireless devices use different radio systems or standards (e.g. WiFi and ZigBee/802.15.4) but their radios do operate on the same frequency band (e.g. 2.4 GHz). To add security, the second wireless device (101) will only accept certain commands if it can detect that the first wireless device (102) is physically close-by. To prove that the first device (102) is close-by, it emits a predetermined energy pattern, e.g., one or more packets (the contents do not matter, while their lengths/time spacing may) using its radio system. At the same time, the second wireless device (101) measures the energy in one or more of its overlapping radio channels to detect that the first wireless device (102) is close by and execute the commanded action.