http://large.stanford.edu/courses/2015/ph241/degraw2/

Medical devices is an obvious potential application for beta decay power. In the past, nuclear power sources were at a major size disadvantage and chemically powered cells can also provide very long service life at such small power draw.

So this definitely isn't nearly as much of a new concept as the media is suggesting. The question is whether they have achieved a compact enough design to be preferential over competing chemically powered cells.

Another application would be cmos batteries for holding memory states. Using ssds in external enclosures is compelling to reduce the amount of time it takes to actually read and write a full drive. But ssds need to be powered every once in a while. If their internal power storage depletes they lose data. Backup ssd drives with an indefinite power source would definitely be a compelling option. I do however doubt if this technology could ever be cheap enough for such an application. The materials used seem rather expensive.