It's a RF signal, so it "can" go through walls .. but I don't have experience with the unit to know how strong of a signal it uses. The "pro" version uses diversity (2 antennae) so it should be more tolerant of crappier signals.
I watched a youtube Video where the Stealth Wireless seems to work flawlessly outside, clear line of sight at 100 feet away. The REviews are either "Great" or "Not Good" ....LOL. ...One DJ has said the unit works, but he wouldn't use them at an event where your reputation is on the line. ...That doesn't make much sense to me...why would I buy the system to NOT use at events I am booking? If I buy the system, I need it to work well at weddings. Sure, maybe there is a once in a blue moon event I book that is outside and I need a speaker way over there and don't want to run a buch of speaker cable, but can't say I've done one of those in a long time. ...I would use the system for when I need a speaker on the other side of a big ballroom, or in another room where running speaker cable just isn't really feasible.
Debating what to do...Not sure if my Lav units are up to the task either.