Thank you both for your insight. I think I'm going to order both, the TIL113 opto and the 4066 and play with them to see which I can figure out easiest on the bench. Schematics and theory are one thing, but my actually getting it to work always seems to be another.
On a quick side note, with respect to "isolation", would it matter -or would your opinion change- that I'm using one power supply (3.7V LiPo 13500mah) battery for the whole package. The phone operates on 3.7V but is only putting 2.65V through the on/off switch. The Lilypad runs fine on the 3.7V as well as the ADXL320 accelerometer which fits into the whole mix. When you speak of isolation, is it becuase the V is different (2.65V @ on/off switch -vs- 3.7V LiPo) or were you assuming I was using multiple different power supplies (ie..5V & 3.7V)?