In the United States there is no requirement to monitor any particular frequency while in uncontrolled airspace. Most pilots monitor the local airport channel. For remote areas maybe 122.9 might get somebody.
Canada has (or had) a neat system where everybody monitored and chatted on 126.7, I think , so inflight help was easy. Been about 30 years or so since I crossed into Canada and with the hassles involved since 911 I doubt I will go again soon. But the common channel for calling anybody nearby seem like a good idea to me.