Options you get:

• Diskless boot (requires main server)
• Low processor requirements
• Moderately low memory requirements
• Compact foot print
• use it to auto dial another network/isp with alternating phone numbers
• when dialing and connected, notify another machine securly that the connection is up
• do limited stuff on the termserver w/o having to log in (i.e. start connection, -HUP init, etc.)
• serial console (no video card required assuming your mb supports it)

Equipment needed:

• Motherboard and CPU (I used a 486/33dx because that is what I had laying around)
• about 8megs memory
• ethernet card
• eprom burner or a floppy controler and a floppy drive
• async cards like:
  • standard two port async cards (16550s recommended)
  • multiport cards like:
    • AST compatible cards
    • Cyclades
    • DigiBoard PC/xe or PC/xi
    • Specialix SI/XIO
    • Stallion EasyIO or EasyConnection
    • or any other card FreeBSD supports
• case and power supply, possibly rack mount with central power supply also works