The Internet tablets happily work with multiple Bluetooth devices simultaneously. For instance, many folks have used their tablets with Bluetooth GPS units while pulling data over Bluetooth connection to phones and typing on Bluetooth keyboards. Connecting to both a phone and headphones should be no problem.

However, the BH-500 headphones want the A2DP Bluetooth profile, and support for that on the tablets is currently...limited. Nokia has not yet provided A2DP support, and while the community has developed stopgap solution until they (hopefully) do, that solution only works with certain media players and devours both battery and processor power. (Search the fora for "A2DP" for more information.)

With the next release of the Internet Tablet OS, Nokia may be including A2DP support. The release is codenamed "Diablo" and folks in the fora have just discovered a way of getting their hands on it early. They'll likely posting messages soon that begin to explore the additions and changes Diablo will bring, so keep a look out to see if official A2DP support will be coming soon.

EDIT: Okaaay. It appears A2DP won't be coming with Diablo.