The Alianza DxB is a portable rugged two-way radio docking case with an additional battery that turns your smartphone into a fully functional multi-band two-way radio. The DxB is able to communicate and work with all major two-way radio vendors.
OKAY short of telepathy this is the best way to talk to babies. We taught my younger brother sign language when he was a baby. We still use some of the signs, usually water and potty, especially in public.