rrdcollect-remote is a Perl daemon that uses the rrdcollect ability to print RRD updates commands to its standard output to do updates from a remote machine using a persistent RSH or SSH connection. Thus you can centralize rrdcollect outputs of several hosts on a single repository with no need for complex and intrusive file-sharing protocols like NFS or CPU-intensive and inefficiant periodic polling like SNMP and so on.
RRD poller allows you to poll RRD files and get the current value of a given data source. Additionally, it implements some advanced checks which can use past values to decide if the current one is out of threshold or not. The main purpose of this tool is to form the interface between an existing monitoring system like BigBrother, Nagios, or Mon and a set of RRD graphs generated by some specialized data collectors like rrdcollect, Cricket, and such. Thus, you can build a very modular monitoring/trend architecture without the need of double polling.