Well, you could either monitor your logs on your VPN device (whatever that may be - not specified), as long as you have the appropriate logging level.
For a traceroute, assuming there's a routing device on the other end of the tunnel you would traverse, you should be able to see the last hop on your end being your VPN device, and then the router or the destination host, as the next hop (and that would indicate you're 'in' the tunnel).
A third option, and more challenging, is having a packet sniffer that knows the PSK, or has the ability to decrypt the session, and analyze the traffic from Wireshark or another packet analysis tool.
HTH!
-Chris
