A watch like you wear on your wrist? I hope this doesn't come across as insulting, but is English your primary language? On forums like this there are posters from all over the world and I'm just wondering if you meant "watch" as in "to look at something" instead of the type of watch that tells you the time.
If you meant to ask if there's a way to quickly check your SMS, email, etc. without having to unlock your phone you'll probably have to jailbreak it. There's an app in Cydia (the jailbroken app store) that allows you to customize your lock screen so you can see different things. I don't have that app because I don't feel like paying for it, but perhaps within it is a setting that allows you to check your things.
If you're talking about an actual watch, have you considered taping your phone to your arm?!