No, the iOS device would need to be connected to the same network that the Airport Express is on. E.g. -- on my iPhone, double-click the home button, swipe left, tap the AirPlay icon, and you're streaming whatever's playing on your phone.
The Airport Express has a single audio out that doubles as an analog 3.5mm out or a mini-Toslink digital out; it isn't a full-sized optical connection.
ht Panasonic 60" ZT60, Monitor Audio: Silver RX6, RX Centre, RX1; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D, Panamax M-5100PM
2ch Sony 32" W650A, Sonus faber Toy Monitor, REL T3, Marantz PM8004, Sony BDP-S1000ES, JVC T-X3 tuner, Apple TV, Peachtree Audio DAC•iT, Panamax MR4300
pc Monitor Audio Radius 90HD, Audioengine D1, FiiO A1
+ Sony 65" XBRX850B, Sony BDP-S5100