Koolspan TrustCall allows users to make hardware-encrypted VoIP phone calls from regular smartphones. In this video I spoke to Glenn Schoonover, a senior sales engineer. Koolspan's encryption engine runs on a microSD form factor device (called the TrustChip) that includes an ARM processor; it must be present in both the sending and receiving phones. The calling application gives users the opportunity to choose between a regular call and an encrypted VoIP call at the time of dialing.
While they were only showing the call encryption app, there are other ways that this hardware-based encryption could be included in mobile device scenarios. Think of an organization telling its employees, "If you want access to our most sensitive data, you have to be using a phone with this chip."