Pulse jet engines seem to be a niche motor without a niche. They were working on this one locally. It was hangered for a short time at my local airport for ground tests(?) and then test flown at the Mojave Air & Space Port.
Like all mechanical engines there is a range of speed that it fits into and it doesn’t appear to have a home at this time. I believe a PDE is limited to Mach 5. The [Blackswift](pulse detonation engine,longeasy) concept aircraft just uses an integral turbine/ramjet engine (look down the page). It is interesting to note that the concept of a rocket launched version was proposed because this is what I came up with as a wag. It makes sense to use conventional boosters to get something in range and then let a remote vehicle poke around from there.