I am a huge fan of mostly everything coming out of Ellusionist.com lately, though there are a few effects here and there that aren't as good as the others. Fortunately, Ringtone is one of the good ones.
In essence, you are changing the spectator's ringtone on their cell phone to a new song--preferably one they didn't already have on their phone. The spectator believes they are the ones who came up with the song randomly, which adds to the strength of the effect.
Here is the key: you must have a combination of guts and technical skill to pull this off. The dream setting for this is to find someone who uses either the iPhone or the exact same cell phone you do. Both are ideal, but not necessary. You just might have to spend a little time in Best Buy playing around with their cell phone displays to learn the key factor you need to know about each phone to make this work. Once you have that one move nailed, the rest is performance.
The "gimmick" that makes this work is nice. I've only had mine about three months but it's held up well and was easy to set up. Even though the demo video shows them going with "The Star Spangled Banner" as their song choice (and the teaching video does the same), you can actually use any song you choose. Set it up once and you are ready to go from that point on. You can't change the song on the fly, but you aren't locked in to anything. You can change it before you go out so you're using a different song every day if you so choose.
Handling is good, and the angles are fairly safe (though you can't perform this surrounded or even for a group that's getting too close). Adam Grace does a great job of teaching you how to handle everything and set it all up. There are several ways to help the spectator to choose the right song, and they are explained in detail. Clean up is safe as well. The best part is that you don't damage or even do anything to their phone that could cause it to get messed up. You're safe.
Pretty close to perfect once you spend time learning the moves you need. It's just that element of possible failure that makes it lose a star. Grace gives you ideas of how to get the information about the phone from the spectator themselves, but it's still a little chancy.