When I spent a summer/winter in Stanley ID, a "friend" reminded me, "There are only two critters that will stalk a man; polar bear and cougar. And there ain't no polar bear in Idaho."
There was an article in some outdoor magazine about a guy to was tracking a cougar with his dogs. I think they got the cat treed, but it was getting late so the guy went back to his cabin. The next day, the cat was gone of course. But the guy saw the tracks went back to his cabin. Sort of an "I know where you live." gesture.
I saw one black bear in the wild while on the Oregon PCT. I had a whistle in my hand but I think I was inhaling so much I wouldn't have enough exhale to blow it. I figure the point of carrying the whistle was to have something to throw. But the bear, about 50 meters away, went his way and I went mine.
The problem with "devices" is the assumption that you can get to them in time. The friend mentioned about carries a pistol in the woods but he has it in his backpack. It seems you have to be constantly "on the ready" - which is not the relaxing paddle adventure I seek out.
If I were in bear territory, I'd adopt the technique of eating meals in mid-travel rather than at camp. I don't mean on the water. I mean pulling over to the shore, having breakfast/lunch/dinner, then continuing to paddle to the campsite.