GEEKMAN  Uh, have you heard of codecs? Just download Perian:

http://www.macupdate.com/info.php/id/22923/perian  
(Version 0.3.4)

GEEKMAN  Apologies, I meant to post this as a review. This corresponds to the comment below.  
(Version 1.2)

GEEKMAN  Yes, this tuner does nothing more than act as a digital pitch pipe. Ironically, I found it to be by far the easiest to tune to out of all the free apps and most of the shareware apps on the site.

Hands-down the best tuner is GarageBand (add a real instrument track, then click the tuning fork in the little time readout panel in the bottom). I didn't want to install the massive loop library for a simple tuner, so this is a usable substitute.

I feel bad about giving this a positive review considering the simplicity, but it really does get the job done so much better than the many automatic tuners out there, assuming you have the ear for it. So, if nothing else, kudos on hitting the small, obscure niche of instrument tuners that actually work.

My one suggestion would be to have the note stop playing when you click another note. Unless there's something I don't know about tuning, it's nothing but an annoyance to have to silence one note before you can hear the other. It'd also be helpful if it could play the guitar repeatedly - I ended up tuning to the violin so I wouldn't have to keep hitting the note button.  
(Version 1.2)

GEEKMAN  This app is amazing in concept, less so in execution. It has serious stability issues on my computer (10.4.10 MacBook Pro). I'm running the 10-day evaluation period now, and in that time it's crashed 4 or 5 times. A rather poor show from an app that people depend on to notify them of server outages anywhere, anytime.

The good news is that this app does what it's intended for, and does it well. I have it checking all my servers, plus my servers' IPs in case of nameserver issues, and (when it's running) it gets the job done quite nicely.

Its processor usage runs around 5% when updating, 0.0% the rest of the time. The memory usage is on the high side, though - 27 MB. By contrast, QuickSilver uses 13 MB (with menu enabled, just like Server Siren) and Growl uses a whopping 7 MB. So I'd definitely like to see this app optimized.

Finally, for the wishlist. I would very much like to see Growl support added. The notifications Server Siren uses are very classy, but Growl is much more flexible and I like to keep everything consistent. An option in the preferences to do this would be nice. What's more, I'd like to see an option to ping a server with near-100% uptime, like Apple.com, before alerting - I don't want to hear that all my servers are down, only to find out it was just my computer's internet that was out.

Server Siren is a nice app and I would certainly buy it if the stability issues were fixed, even though there are many open-source apps (even smaller projects) with a more extensive feature set.

Finally, I'll close with a link to an app with a similar purpose, although somewhat complimentary to Server Siren. I'm still working out how to set it up, but it should be interesting to get it in action.

http://www.bixdata.com/  
(Version 1.1)