Surely is just so, hypocondria :-), and yes its far less and short, but is continously and all day.... Isn't there any other wireless technology that works on daylight and it's not based on radio? Too much to ask?
All wireless technologies are implemented, and particularly the frequencies at which they operate, taking into account any and all impact on an individuals health. The public concern is so strong that no manufacturer puts equipment on the market that exposes them to any potential health liability. There has been a considerable amount of research into short and long term effects on health - recently driven by public concerns over mobile phones but also previously by people involved in the design and implementation of high power radio equipment (such as broadcast, radar and communications). There are a couple of resonant frequencies which if used could cause health consequences but these are avoided in the design of equipment. For the most part the level of exposure the body receives from radio transmitters in portable equipment is negligable compared with other risks that exists - consider that all portable equipment is battery powered and, therefore, unable to sustain the transmission of any powerful radio single for any amount of time.
You make reference to operation in daylight - you are more likely to suffer more harm from standing in the sun for an hour on a sunny day than you are from using your mobile phone/ flash trigger for the same duration of time. The suns power when it reaches you (and ability to damage your health) is much stronger.
Continuing to use the reference of mobile phones (as a reference compared with flash triggers), there are well over a billion mobile phones in use around the world at the moment. From these users and in many studies there has been no demonstrable health risk associated from this type of technology.
People have a right to be concerned - there is still some debate, for instance, about health implications for people living near high voltage power transmission lines - but for low power hand portable transmitters there is a large body of research which indicates that there is no identifiable health implication associated with the use of such devices. This can also be extended to wireless area networks that transmit at similar frequencies and low power.