This is as safe as it can be. Obviously, there's fire involved- so there's always some danger. I didnt want a capsule or reservoir of flammable liquid on me, so a stream of fire is out. This little guy however, will be a fun little toy.
No residue, depending on the load, I can get around 20 ft, but it burns so fast it appears to only go a few feet sometimes. It's wireless, so I can trigger it from wherever, hence standing back for the first few.
To be honest it would be pretty easy to have this work. You could get the guts of a powered water gun or spray gun that shoots X feet and fill the resorvoir with alcohol. Personally I would get the powered spray gun because it would be shorter ranged...bigger effect...and easier to control. The alcohol would be flammable but not nearly as explosive.