Seriously though, there are a few things to be aware of. Fall is rutting season so the damn things are even stupider than normal. They are prey animals so they like cover...they will try to cross the road where the foliage is closest to the road, so slow down where the bushes are close to the road. If you spend time bicycling at low speeds on your favorite moto roads you'll start to notice many of the tiny deer trails many of which come down very steep enbankments. Maybe it leads to a water source? So think about those things.
RE: deer whistles, I do have em on my bikes but don't know how well they work based on past experience. But reading up on them I found this, which does seem more promising. Also they have some good info on their site, more things to be aware of RE: deer behavior etc.
https://xp3hornet.com/faq/
I actually made one myself back in the day for a project while studying electronics at College of Marin. Much smaller, lower powered than this hornet thing.