This is from the Minnesota Air Medical Council, I'd assume this may be consistent across many states besides the midwest -
When Landing at a scene where there may be a possibility of more than one helicopter (other EMS, news, or State Patrol) monitor the air to air helicopter frequency of 123.025, and announce your position.
New media helicopters in the twin cities area and also the State Patrol helicopters monitor 122.75. Contact these helicopters on this frequency if theya re in your vicinity.
SD, ND, WI statewide Air to Air Helicopter 123.025