With IPHost Network Monitor you can run simple snmp requests against a HP device in your network.
slipInOctets
slip In Octets
1.3.6.1.4.1.11.2.3.9.3.1.4.28
The number of octets received over the serial interface while running SLIP.
Back to hp-700rx MIB page.
IPHost Network monitor allows you to monitor slipInOctets on Hewlett Packard device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco routers right now.