Ability to use custom fields as dynamic fields in templates

By default (and as the response template example in Callbell shows) the dynamic fields {{firstName}} or {lastName}} can be used. It would be great if templates could take information from contact card custom fields as well
** Example: Hello {{firtName}}, this message is to remind you that we have a meeting scheduled for {{Meeting Date}} at {{Meeting Time}} **- ("Meeting Date and " Meeting Time" would be the custom fields used)