There is no access to specific statistics in the email creation - you can show the raw data (##HISTORYDATA##), but not the accumulated totals.
Most alerts are set up for some period of latency or packet loss, so most alerts have known thresholds for packet loss / latency (alerting on packet loss walk-through here:
http://www.nessoft.com/kb/63). Because the alert doesn't fire until you get to this specific known level, you can put your configuration as part of the subject of the email or the body - "$dest has > 60% loss for last 5 minutes!" as a subject line, for example.
Some people also do progressive alerts - where you set up one alert for 5 minutes (or however many samples you normally collect in 5 minutes), and another one for 10 minutes - that would notify you as the outage increases in length, and then couple that with a back-up event for one or all of them.
As a related note, there are some best practices for alerting here - you may have already seen them, but just wanted to share:
http://www.nessoft.com/kb/81Please let me know where this leaves you.
- Pete