I'm not sure but in 15 seasons I've never worked a game without a visible play clock. It's my understanding there are some without one though.
There's absolutely no doubt, equipping mouse traps with nuclear warheads will effectively eliminate any, and all, mouse problems, but whether that solution is worth the collateral damages is highly questionable.
Do we need a "Play Clock" at the High School level? If the idea is to contain the length of actual playing time, is there better, more practical, simpler ways to deal with that issue (just as, if not more, effectively)?
Technology, applied for a beneficial reason, can be helpful. Technology applied, for the pure sake of having the latest and greatest or "being like the pros" is silly.