You can integrate SAP WF's with your Notes-mail system, using an agent to tell the users that now they've got a work item waiting for them in their inbox. 

or

by changing the priority to '1 express' and the other person will get the Pop-up telling them that they've got something in their inbox, BUT ONLY IF they are LOGGED ON at the time of receipt. 

If they are not logged on, they don't get any message at Log-on.

The popup for unread items in the SAP Inbox can be activated using workflow customizing (SWU3) 
->Maintain Addl Setting and Svces ->Activate Send to Objects and HR Objects. 
Check off "No notif of unviewed mails" on the 1st tab. 

or

you can considered creating a secondary method which, if the user is in your non-Notes integrated plant, sends a notification as an external email. This whould use SELFITEM - Sendtaskdescription, and should not have any trouble being sent to the net using Connector - the only question is do the users at your new site have the ability to receive emails. 

or 

You can also use SAP MAPI, Exchange Connector or Desktop Workplace to notify them by email when a new Work Item arrives. 

Get help for your SAP WF problems 
Do you have a SAP WorkFlow Question?

SAP Books
SAP WorkFlow Certification, Interview Questions and Configuration Reference Books

SAP WorkFlow Tips
SAP Business WorkFlow Tips and WF Discussion Forum

Best regards,
SAP Basis, ABAP Programming and Other IMG Stuff
http://www.erpgreat.com