FMAXWELL  If you think that USB ports are "precious," you need a cheaper hobby or more income. The computer stores practically give away USB hubs. Every wired Apple keyboard has at least one.

If you are so concerned about losing the key (but not forgetting a password, apparently), then make a duplicate USB key. It's not like USB thumb drives are expensive. Small ones can be had for just a few dollars (I picked up some 256K drives for $3.99, threw away the drives, and kept the lanyards, which is all I bought them for).  
(Version 1.6.1)

FMAXWELL  HABANITA:

I am sorry that you took my comment personally, because that is not how it was intended. Just the opposite in fact: A stranger is giving me an app that is asking for my gmail address and password. I don't know you. I'm suspecting that you're probably a good guy, but I am a computer security professional and I'm concerned.

You will note that another reviewer, BCARTER, wrote: "Not really interested in supplying my Gmail username and password to this app/developer."

I did not examine the code line-by-line (and neither does Softpedia, which has a huge disclaimer in their terms of service).

I did note that the package includes an encrypted SMTP module (smtp_tls.rb) and I'm thinking to myself "if this thing is doing everything through the gmail web interface, why is there an encrypted SMTP module in here?" Your load_prefs script has been saved runnable, meaning that the Apple script editor can't open it. It doesn't appear that the application is using Apple's keychain, so I don't know if my account name and password are being saved in a secure manner.

Sorry if all of this angers you, but I'm trying to do my due-diligence here.  
(Version 1.1b3)

FMAXWELL  Rather than using a standard SMTP protocol for sending, this application only works with gmail. If you do not have a gmail account, the app will not work for you.

The application asks for your gmail login and password. This is a tremendous security concern. Even if you use a firewall and limit the application's access to gmail, for all you know, it is logging on to gmail and sending your account login information to the author -- or sending him copies of e-mail from your gmail account.

Until/unless the author makes a version that works with standard mail servers (rather than proprietary gmail servers) I recommend that you pass on this one.  
(Version 1.1b3)