We always enjoy bringing readers details of new and in-demand apps for their mobile devices and today we have information of the Tempo app for iPhone, iPod touch and iPad. This is a productivity app, like a virtual assistant and bills itself as the ultimate smart calendar. One snag though is that, similar to the recent Mailbox app, this app is available only on reservation. Read on for more on the Tempo Smart Calendar App for iOS.

This app certainly looks pretty impressive and I’m thinking of joining the reservations myself even though the process is almost enough to put me off bothering. It’s an enriched calendar app using cloud-based intelligence so has more depth than most calendar apps as it analyzes past history, contact frequency and more.

It offers a variety of resources so you can use it for connecting to Foursquare and Yelp, send a friend a birthday greeting on Facebook, access travel times, get directions and parking information, open documents, send pre-populated texts and emails, use Siri, check your flight status and much more and we reckon this app could soon become invaluable.

The problem is that this Tempo Smart Calendar app seems to be making such big waves that in efforts not to overload the servers access to the app is now available on a first-come first-served reservation basis. Regular readers may remember this also happened on the recent Mailbox app for iOS devices where we asked if this was some kind of gimmick or alternatively a clever solution to heavy demand.

We also gave readers a review roundup of the Mailbox app and most reviewers felt this new idea of reservations for an app was a drawback, with one reviewer even describing it as a clever marketing ploy to make people wait for something as they then think it must be really good. Back to the Tempo Smart Calendar app and if you want to join the reservations then download the app to reserve your spot at this iTunes page. It’s a free app compatible with iPhone 3GS, iPhone 4, iPhone 4S, iPhone 5, iPod touch (3rd, 4th and 5th generation), and iPad running iOS 5.0 or later and the app is optimized for iPhone 5.

To be fair although we think this looks like a very useful app we’re in two minds about the idea of the reservation system. Although it has merits if it does indeed prevent a very popular app from overloading, we still feel it would be better if the app was built to cope with demand in the first place. We’d like to know your thoughts on this. Are you waiting for the Tempo Smart Calendar app or are you heading for the App Store now? Do you think reservations for apps are a good idea or rather a stunt to promote the app? Let us have your comments.