I would suggest the HP-11C. It's available on ebay, and is not $15 cheap, but it is an RPN programmable scientific, of less complexity than the HP-48. I am an RPN fan, so I would go the extra mile to get an RPN calculator.
We never liked the choices available for secure email for mobile devices, because no email client with PGP encryption was available for smartphones. Instead, we had to install PGP Universal, which is a server-based version of PGP, designed for enterprise environments, which does the PGP encryption and decryption on the server, with PGP private keys stored on the server. Not a good architecture for consumers in today's climate. We strongly preferred to do PGP on the client side, but we were a long way from having a PGP client for mobile devices. And even if we had a PGP client, we would still be stuck with email metadata exposure on the servers, even with the message body encrypted. That's why we were unhappy with Silent Mail, and why we were discussing a phaseout for some weeks before these events. The Lavabit event made it clear we could not put it off any longer. --Phil Zimmermann (spelled with two Ns)
We in fact do publish the source code for Silent Phone and Silent Text. -Phil Zimmermann
It says "Consider a roof top coating on your car with this new material." I don't see why anyone would want that. The coating would saturate with CO2, then it would absorb no more. And it would remain on your car for years, uselessly full. How is this useful? Alternatively, what if it absorbed the carbon, then released it later, so as to be reusable? Why would that be any use as a rooftop coating? The release of the carbon would go back into the atmosphere. The whole idea of a rooftop coating for your car is pointless. Surely the scientists who developed it would not say that. Is this from a marketing person?
Why did Google even have Wifi interception equipment on their vehicle? I see no legitimate reason for this capability for a vehicle designed to take photos for street view. Oops-- we accidentally gathered information using equipment that is designed to gather this information?
I wish the article spelled Zimmermann with two Ns.