Measuring fields from mobile or cordless phones
Mobile phones rarely expose you to high levels when not in use, but can expose your head quite highly when in use. It is advisable not to keep your phone in a pocket next to your body unless it is turned off (there is no exposure at all from a turned off phone). Hold the phone away from you when sending a text message as it works at high power to do so. It will also expose you to signals when switched on and receiving text messages.
Ordinary cordless phones give off a similar amount of electromagnetic radiation to a mobile phone when in use. Unlike mobile phones however, almost all models emit radiation constantly even when they are in standby on their base units.
The best way to check for radio frequency exposure levels (caused by most wireless devices) is to use a suitable instrument such as an Acoustimeter. You can purchase this instrument or another, cheaper (but still highly accurate) alternative such as the Acousticom 2.