Trait for peekable iterators

There's some useful methods on core::iter::Peekable, but those require making an adapter around your trait and then you can't ever get the original iterator back. Since many iterators could peek at their next element, it seems to me like it would be useful to make a trait that allows calling those methods without needing to use the wrapper. I envision the trait looking pretty similar to the current Peekable struct, minus the methods that require mutating (peek_mut, next_if_map, next_if_map_mut)...