Penango - secure emails
Penango is a successor to free Firefox extension Gmail S/MIME, which let's you send encrypted emails using Gmail, Google Apps mail and Zimbra. As Google Apps or Gmail is not HIPAA complaint though it is running over Secure HTTP (HTTPS) protocol.
It comes as a Firefox, Maxthon and Internet Explorer extension.
Unlike Gmail S/MIME extension for Firefox, Penango is not going to be free but if you want to send signed emails (using email certificate) which are encrypted then I don't see any other alternates for Gmail or Google apps users.
See Penango's seamless integration with Gmail service, you can easily setup this for your Google apps email account too.
Penango's seamless integration with Gmail
Here I am providing you download information I have received while signing up for trial, you can either go and sign-up yourself or download Penango extension for your browser.
