I use a Logitech Harmony 676 to control my entertainment system including my PVR. The PVR system contains 2 Hauppauge PVR 150's using the IR receiver plugged into 1 of the PVR150s. You should be able to check out whether the harmony supports the PVR card and IR combination that you plan on using on logitech's www site.
just go add the 150 as a device on the harmony site and select the ir interface in gbpvr. i use usb-uirt and mapped the buttons in the settings (select usbuirt on the list) on the dvd&remote tab.