The watch command

watch -n1 ' ps aux | grep what_you_want'

Something interesting when combined with svc:

cd /etc/service # or wherever svc (supervise) is installed
watch svstat *

It will monitor every 2 seconds the state of your service.

Monitor the queries being run in real time:

watch -n 1 'sudo -u postgres psql --tuples-only --command "SELECT datname, procpid, date_trunc(\$\$second\$\$, age(current_timestamp, xact_start)), current_query FROM pg_stat_activity;"'

Source: http://kevin.deldycke.com/2011/10/postgresql-commands/