With Gmail, is there some way to do that check?
You can try a service as SpyPig to sent you a notification when your email has been read.
SpyPig is a simple email tracking system that sends you a notification email as soon as the recipient opens and reads your message.
It works with virtually all modern email programs: Outlook, Eudora, Yahoo Email, Gmail, Hotmail, AOL Email and many others.
Both you and the recipient must use an HTML email, not plain-text or rich-text email. Visit the Requirements & Limitations page to learn more about SpyPig.
Kudos to labnol.org for the suggestion!
Not if you use the web ui. I think (but am not certain) that it would work if you use a desktop client that supports it.
See here for details about why it doesn't work and is generally unreliable: http://knol.google.com/k/read-receipts-in-gmail#
Similar to the suggestion by @Ivo, whoreadme is, you guessed it, a tool that can track who has read and forwarded your emails.
WhoReadMe is embedded a transparent tracking image into your HTML e-mail. The image is assigned with unique ID and stored in WhoReadMe server. Once your recipient opens your e-mail, tracking image will be loaded from WhoReadMe server. Therefore, WhoReadMe is alerted to send you notification.
However, it still has the problems associated with this method of tracking if an email has read in that generally, people will not have their email client set to download images by default.