First the bad news: I'm pretty sure there's no way to trigger the S120's shutter remotely because a) Gordon's review
specifically notes the lack of wireless capability, and b) I'm not aware of any wired remotes for Canons point-and-shoot models, mostly just DSLRs. (Although, the RS60E3
also lists the G1 X and G16 as compatible. So you might consider one of those cameras.)
Or, as long as exact timing isn't necessary, you should be able to get comparable results with the self-timer function (which Gordon's review does briefly mention, so I'm assuming the S120 has one).
HTH - Mark