or, depending on what exactly you want (see below)
var i = $("#panel :input");
the > will restrict to children, you want all descendants.
EDIT: As Nick pointed out, there's a subtle difference between $("#panel input") and $("#panel :input).
The first one will only retrieve elements of type input, that is , but not , and elements. Thanks Nick, didn't know this myself and corrected my post accordingly. Left both options, because I guess the OP wasn't aware of that either and -technically- asked for inputs... :-)