That's a good trick, depending on the vocal, song, etc. I occasionally use a chorus plug on a send, with the mod set to fairly deep and slow. That allows you to blend the vocal stereo effect, and control the width. You can insert a delay ahead of the chorus, too, if you want to delay the pitch shifted bits a little, to retain some clarity and improve mono compatibility. You can also put a LPF on the channel, if the consonants are sounding too weird.
I used to use a plug designed for pitch shifting, but it wasn't compatible with the Intel Macs, so had to retire it!
You can also use this trick on bass guitar, if you want a very wide deep bass sound. Again, mono compatibility will be compromised, so some eq may be necessary!