I feel your pain... I run for a local running club, there are couple people that just yak on and on. Even yelling "SHUT UP AND RUN!" has no effect. Not sure that anything suggested above would work. Runners are uncouth, smelly people. Sweat and pee would not deter many. Our singlets stink to high heaven. We are masters of the Farmer's Blow. The most intimate details of your latest injury is met with genuine interest. The Talkers even yak away during 400 meter interval training, to the uninitiated, this is way above the "conversational" effort recommended in Runner's World magazine. We're talking Republic of Anaerobia here.
The one and only thing that I've found to be even moderately effective in these extreme cases is to fight fire with fire: you have to actually be able to talk more than they do, they will eventually get bored with listening to someone other than themselves and move on to someone else's ear. This is easier said than done when in extreme oxygen debt.