I hold a lanyard whistle in my hand. It's never in my mouth unless I'm blowing it. So the whistle control is the same as a finger whistle, except it's *in* my fingers instead of *on* my fingers.
Doesn't that tie up one of my hands? I guess. But whenever I need both hands, I just let go of the whistle. And besides, I never need both hands at once except between downs. The iron cross before the down, and two-handed signals after the down. Letting the whistle dangle is not an issue.
I keep it in my left hand since I'm a right-handed flag-thrower. Unless I have to punch back a receiver with my left hand, in which case the whistle is in my right. If a blow-and-throw happens, it's pretty quick to stick the whistle in my mouth and then grab the flag.
The trick for me, though is: I use a longer lanyard than usual.
With a longer lanyard, I can hold the whistle in my fingers while keeping my arm in a normal-looking position near my waist. There's no need to constantly hold my hand up like I'm thumping my chest. While running, I can keep a normal stride and still swing my arms.
It's a breakaway lanyard in case it gets caught on something (which has never happened to me).
So that dispenses with almost all of the drawbacks of a lanyard. Meanwhile, I avoid all the well-known shortcomings of a finger whistle:
I can give two-handed signals. Seriously, nobody should be giving one-handed signals. If your finger whistle is loose enough, you can stick it in your mouth and remove it from your fingers, and some guys do that. But what they can't do is let the whistle drop after they're done blowing it, and still have their hands free.