You can both retrieve and post E-Mail Templates to Heap CRM via the WebHook. Just set "list" to "eventtemplates" (there is an example under your help section). This will result in something like:
"subject":"[event name] [event location]",
"body":"[event description]\n\nSome more text\n\n[convert to: lead]"
Additionally, you can create a new E-Mail Template by posting to (or including JSON) the variables "subject" and "body".
Because this addition is to the WebHook, you can use this info in a whole bunch of places including Google Spreadsheets, your website, or really anywhere you can process JSON.