This is what I use to;

SQL job which runs a script every 15 mins and checks for latency. The job does the following:

1. Post a tracer token at the publisher

2. Wait for delay for token to make it to the subscriber, delay should be more than the latency

3. Catch the tracer token at the subscriber and if the latency exceeds the limit send email/page..

This link pretty much has it covered, hope this helps 🙂

http://msdn.microsoft.com/en-us/library/ms176091.aspx