VPNs provide protected network connections. If your remote board does not have a network connection, then a VPN will not be able to give you an interface to the board. If the remote board -does- have a network connection, then the VPN is not -necessary- to access the remote board.
You would use a VPN if the remote board -does- have a network connection but you need to improve the security of that connection.
There is one other circumstance: if the remote board has a network connection, but that network connection relies upon multicast or local broadcasts or upon non-IP protocols such as IPX or appletalk, then -some- forms of VPN connection can join the remote network and the local network as if they were all local to each other.
If your remote board does not have a network connection but does have a serial interface (RS232, RS422), then there are companies which make equipment which provide "remote console" connections -- network addressible serial ports. The price of those devices depends a lot on what kind of security you need for the remote connection. If you need an encrypted connection to the "remote console", then you might find it most cost effective to use a remote console device that does not have a lot of security, and then to use a VPN to secure the connection to the remote console device. For example, you might combine a Linksys BEFVP41 with a Synaccess Networks NPC-22.