I work from my home and do not get cellular service where I live, but
am online all the time. Is there a service out there that could
provide an email notification to me when I have a new cellular voice
mail message to listen to? I use both Sprint and Nextel cell phones.
Thanks.

If you don't get any service where you live, then your phone won't be
able to detect whether or not there's a message waiting until you go
into an area where you do get coverage.  Until you're in a place where
your phone's got reception, the network has no way to communicate to
the phone that there is or is not a message.

Without having access to your carrier's internal min/imei monitoring
network (you don't), the only ways to check if you have messages are
to either look at the phone (when it's in a coverage area), or check
your messages from a different phone.

Try www.gotvoice.com

It's free and would do exactly what you're asking about.