Don't use a wireless baby monitor.
Healthy HouseTM TechTip
Cordless baby monitors emit a very significant amount of wireless radiation that is well into the "extreme concern" range per Building Biology standards. It doesn't matter if the baby monitor is an audio-only unit or also capable of video, these wireless units communicate via RF (radio frequency) and emit radiation. The newer breathing and heart-rate monitors for babies that operate wirelessly are also concerning from an EMF perspective.The easiest way to protect your baby is to avoid the use of wireless monitoring technology.
There have been a number of new wireless monitoring products that have been recently launched to “protect” your vulnerable baby. The only problem with these technologies is the oversight of the health effects due to wireless radiation exposure. Most of these products market signal strength as a good thing.
If you absolutely need to use a wireless monitor, your best solution is to purchase an analog model that transmits at a lower frequency. Position it to be as far away from your baby as possible.