diagnostics.js

(function(d){
	console.log("Wrapping dojo.connect/subscribe");

	var dc = d.connect, 
		ddc = d.disconnect, 
		ds = d.subscribe, 
		dus = d.unsubscribe, 
		uniqueHandleId = 0, 
		handleIds = {};
	var handleData = { connect: 0, disconnect: 0, subscribe: 0, unsubscribe: 0 };
	d.connect = function() {
		handleData.connect++;
		var hdl = dc.apply(d, arguments);
		hdl._debugId = ++uniqueHandleId;
		handleIds[hdl._debugId] = "connect";
		return hdl;
	};
	d.disconnect = function(handle) {
		if(handle) {
			handleData.disconnect++;
			var hid = ("_debugId" in handle) ? handle._debugId : null;
			if(hid) {
				if(hid in handleIds) {
					// console.log("disconnecting recognized handle: ", hid, handle);
					delete handleIds[hid];
				} else {
					console.warn("attempt to disconnect previously disconnected handle? ", hid, handle);
				}
			} else {
				console.warn("disconnecting handle without debugId: ", handle);
			}
		} else {
			console.warn("disconnect given falsy handle: ", handle, typeof handle);
		}
		return ddc.apply(d, arguments);
	};
	d.subscribe = function() {
		handleData.subscribe++;
		var hdl = ds.apply(d, arguments);
		hdl._debugId = ++uniqueHandleId;
		handleIds[hdl._debugId] = "subscribe";
		return hdl;
	};
	d.unsubscribe = function(handle) {
		if(handle) {
			handleData.unsubscribe++;
			var hid = ("_debugId" in handle) ? handle._debugId : null;
			if(hid) {
				if(hid in handleIds) {
					// console.log("unsubscribing recognized handle: ", hid, handle);
					delete handleIds[hid];
				} else {
					console.warn("attempt to unsubscribe previously unsubscribed handle? ", hid, handle);
				}
			} else {
				// console.warn("unsubscribing handle without debugId: ", handle);
			}
		} else {
			console.warn("unsubscribe given falsy handle: ", handle, typeof handle);
		}
		return dus.apply(d, arguments);
	};
	d._connectReport = function(){
		var data = dojo.delegate(handleData, {
			connectDelta: handleData.connect - handleData.disconnect,
			subscribeDelta: handleData.subscribe - handleData.unsubscribe,
			windowUnLoaders: dojo._windowUnloaders.length,
			onLoaders: dojo._loaders.length,
			unLoaders: dojo._unloaders.length
		});
		console.log(d.toJson(data, true));
	};

})(dojo);

Should be loaded anytime after dojo.js (the sooner the better). Get the report from the console e.g. > dojo._connectReport()

I edited to reflect an earlier, simpler version and which I was sole author of.