Child program using parent program's transaction?

I work with a system designed as lots of little cooperating worker
programs, with boss programs that... well, boss the worker programs
around.

Boss and workers all use the same database.

Sometimes it would be convenient to have a boss start a transaction
and then have the workers do their work in the context of that
transaction.

Each time, I've decided that since I don't know how to do that, that I
never really wanted to do that. You know how it goes.

Today, it would once again be convenient to have an exec'd program do
its work in the context of its parent program's transaction. So,
before I once again decide that I don't actually want to do that, can
you tell me... is it possible? And, would any sane person do it?

We're using Linux. All of the programs are written in Ruby 1.8, using
the venerable (or is it just ancient?) pgsql library.