As seen in Nintendo Wii official website, wii.nintendo.com , and many other places, the first batch of Wiis came with rather flimsy wrist straps for their Wiimotes. Many incidents were recorded of users letting go of the wiimote while playing with enough force to have the strap break.
If you are the proud owner of one of the first Wiis delivered, there's good news. Nintendo is shipping new and improved wrist straps. Just go to the official Wii website, and fill out the form. They will promptly ship up to four straps depending on your needs. The only requirement is to have your Wii serial number so they can verify whether your unit was shipped with the old straps. The shipping should take about 5 to 9 days according to the Wii website.
Once again the website is wii.nintendo.com
That is all.