An interesting question that caught my attention dropped into my Hardware 2.0 mailbox over the weekend.

"The more I use my iPhone, the more I feel like I'm sending and receiving a lot of important -- and potentially sensitive -- data over WiFi and 3G connections. Are there any apps that I could install onto my iPhone that would allow me to encrypt selected email and voice communications?

"I like to be able to do this without jailbreaking my iPhone."

Apple promised that "there's an app for just about anything" and, true to that slogan, there's are apps that allow you to do exactly what you want.

One of the best email encryption apps available from the App Store is called Enlocked. This app easy-to-use allows you to send and receive secure email encrypted using PGP which encrypts emails to the PGP/MIME standard. If you already have set up a working PGP infrastructure you can continue using your own keys and infrastructure for decrypting received encrypted emails.

Enlocked easy to set up, and work with all the popular email providers including Gmail, Yahoo Mail, AOL, and Microsoft Live.

Enlocked is a free, and there are versions available not just for the iPhone and iPad but also Android, Outlook, Chrome, Firefox, Internet Explorer and Safari. There's a version for BlackBerry in the pipeline.

That's the email secured, now for the voice communications, and this is where things start to get complicated -- and expensive.

To encrypt voice calls you not only need an app, but you also need to sign up for an encrypted voice service. One company that offers both is Cellcrypt, which offers government-grade security for protecting sensitive voice calls against interception..

Cellcrypt uses public key cryptography, and each phone running the software -- Cellcrypt supports iOS, Android, BlackBerry and Symbian -- has its own private key stored only on the device. When a call is made, the two devices exchange a secret session key, which is subsequently erased when the call ends.

Voice data is then double encrypted, first using a 256-bit RC4 algorithm and then again with a 256-bit AES algorithm. This encryption can a delay of about one and a half seconds when using the slower GPRS networks, but this drops to 150 milliseconds when using WiFi.

Like the app for encrypting email on iOS, the app for encrypting voice calls is free, but the encrypted voice service that you need to make it work is far from free. In fact, it comes with the very enterprise-level price tag of $1,600 per year, per device.

Depending on your budget, you might want to make do with just encrypting email communications.