radios are nice, but not needed in most cases I think. Throat mikes are the way to go if you are going to use them though. The vibration in your vocal cords helps eliminate the ambient noises like chainsaws etc. so your voice is clear to the others on your channel.
For the most part, its still going to be dependent on the dynamic between you and your ground crew.
I look before i cut and make sure my groundguys are not in my drop zone, and they make eye contact with me before entering it. We usually nod if its safe to enter/safe to drop if we cant hear each other. Mine are smart enough not to run in when they hear my chainsaw, but they can usually tell the difference between when I'm making a notch before I cinch my rigging knot and when I'm making the cut thats gonna drop it. If it's being rigged, I make my notch, kerfs, or undercuts, tie/cinch/set the rigging, make eye contact with the ground guy, he nods letting me know hes ready, and the last cuts made.
When I have a question about whether or not I'll have room to bring a peice down in the available space, I'll making a cutting motion with my hands on the spot on the branch where I want to make my cut and he'll give me a thumbs up or not.
Usually not that damn difficult if you have competent ground guys that have their head in the game and want to work.
Radios are nice sometimes but No amount of technology or radios are going to make up for a lack of experience, intelligence, and work ethic. Just saying.