S.F.
These things are just like cell phones and such that transmit signals thru 'invisible' satelitte technology. If they were dangerous there is unfortunately nothing that you would be able to do to get away from them. Signals are flying thru the air constantly
I can totally relate to pregnancy fears though so dont be upset if someone tries to make you feel silly for wanting to do all that you can to protect your precious baby
Good Luck and Congrats