The following Google Apps Script will display the unread Gmail counter for your mailbox to anyone on the Internet with a simple URL.
The count is published as text but you may use other formats (ContentService.MimeType) like RSS, JSON or even CSV and feed this data into other system – like tweets or even another spreadsheet.
/* Gmail Counter by Amit Agarwal */ /* Published on 06/17/2013 */ function doGet() { var cache = CacheService.getPublicCache(); var counter = cache.get("gmail-counter"); // Cache the counter to stay within the Apps Script quota if (!counter) { counter = GmailApp.getInboxUnreadCount(); // Cache the counter value for 20 minutes cache.put("gmail-counter", counter, 1200); } // You can customize the output message counter = "There are " + counter + " unread messages in my Gmail Inbox." // Output the result in plain text format return ContentService.createTextOutput(counter) .setMimeType(ContentService.MimeType.TEXT); }