I'm curious, when would you look at the dipstick to check temps and why? It would seem that unless you are looking at it constantly or its within your line of sight, it isn't really going to do much for you.
If you park the bike and then get down to check it or look down to see it, that doesn't have too much meaning. I guess you could shut off the engine but that might be tough in traffic and by the time you read the gauge and realized it was too hot, who knows how long it was running that hot?
If you are concerned with temps wouldn't a handlebar mounted gauge be the way to go?