Absolutely- our lack of such is a common point of issue when folks are considering using or migrating to PostgreSQL.
Not sure how similar my situation really is, but I find myself wanting to have indices that cross non-partition members of an inheritance hierarchy:
create table t (
id int,
primary key (id)
);
create table t1 (
a text
) inherits (t);
create table t2 (
b int,
c int
) inherits (t);
So "t"s are identified by an integer; and one kind of "t" has a single text attribute while a different kind of "t" has 2 int attributes. The idea is that there is a single primary key constraint on the whole hierarchy that ensures only one record with a particular id can exist in all the tables together. I can imagine wanting to do this with other unique constraints also.
At present I don't actually use inheritance; instead I put triggers on the child tables that do an insert on the parent table, which has the effect of enforcing the uniqueness I want.