Like what rigmaster said, micro usb and Bluetooth adapters for iPhone or iPod docks are available. The only thing is, android OS ice cream and below doesn't have audio through usb so buying a usb adapter might not work unless the android device is running Jellybean. Even if it is running Jellybean, I haven't seen anyone actually use a usb dock for JB androids yet.
Safest bet would be to buy a Bluetooth adapter like this one.
Pear Dongle Makes Any iPod Dock a Bluetooth Speaker | Gadget Lab | Wired.com
Either that, you'll have to wait until android docks with usb audio start popping up like the one below.
Gear4 Android Dock – Introducing A New Type Of Audio Connection On Android Devices « StartupTunes