There is a nice table that shows, that Americium-241 has low power density, but it's half-life is 432 years. It also mentions that the real reason, why this is interesting, is because Am-241 is a byproduct and a pure isotope that can be used without refining.
It's not that simple. The energy per event varies by orders of magnitude depending on the specific transition (even within given particle decays, the energy of the emitted particle varies), also the number of atoms per volume or mass varies depending on material.
It has to first be separated from the rest of the actinide waste, which is very challenging, as they're chemically similar elements. Previously this had to be done with a centrifuge (separating by mass), but a lot of research effort has gone into developing more practical chemical refining methods.
They were referring to a photoelectric smoke detector vs ionization types. Both are still available but photo is much more common now days. They look exactly the same exterior wise, but it works by having a tiny light box where smoke goes in and changes the light the sensor is seeing. They can still cause false alarms because they are sensitive to dust and particulate matter, but they operate on intelligent addressable systems now which can adjust their sensitivity to some degree over time.
Sounds like an americium-powered RTG to me, albeit not a particularly powerful one.
As I understand it, the practical refinement of a significant amount of Americium from waste is the breakthrough. But that doesn't win hearts and minds like a 432 year space lightbulb.
That is the idea. Plutonium RTGs are very hard to get by. As in only the U.S. have a few such RTGs in stock and I am not sure they are producing new ones.