the signal doesn't increase when you dial an emergency number.
Turning on and off in an sos pattern would be useless as the cellphone will just make its first ping once powered up then ping at regular intervals afterward so you can't really make much of an sos pattern unless you spread it out to minutes for each dot or dash and then no one is going to listen to one frequency long enough to notice.
The pings are not to help the network locate you while sending and receiving calls, they have complex protocols based on the signal strength during the call for this, the pings happen while your not making calls so the phone can check signal strength to switch between cell towers.