What would be absolutely brilliant is annotations as well.  ChessDB has annotations, but they come up in a nonscrolling alert window, so anything more than 20 words or so gets cut off.

@TheBenzinator: I don't have any intention for Android development right now - not owning an actual Android device and having to learn the Android frameworks and learn more about Java just makes it impossible for me at the time.

@pdt4aye: Cool!  Glad it's out with variation support!  I bought ChessDB a long time ago but never really found a use for a database application without variations.  I've had some trouble with large databases, though.  I guess PGNs aren't really an ideal database format for a serious database, unfortunately.

@Keyif: The website looks nice, but there's no substantial information!  Will it support variations?  Is it implemented in a way that it's not really distracting and makes playing through games reasonable?  What else does it do?  Does all additional content have to be purchased in-app or can users upload their own chess stuff?

What about Android phones?

ChessDB, a chess database app that I created, recently submitted an update to the app store that includes the ability to play variations. Its still waiting for Apple to approve, which might take a while though because of all the iPhone iOS 4 apps being submitted, but it should be approved by Apple within the week.

maartenderie:

I agree, if only chesstempo.com made an app!

This app is what you are looking for.

http://www.playsmartchess.com/index.html

A database app in development.  The variations already work.  I'll be adding support for annotations and NAG - I'm going to start work on that today, but I expect it might take a week or so to implement (as well as cleaning up the GUI).  Ideally I'd like to come up with an application that can serve as like a Chessbase mobile; for now, I plan on finishing my PGN reader (read only) and offering it up on the app store for free and then offering something to edit PGNs (and maybe chessbase files?) later for pay.  

I don't have any intention of designing a playing app, though if any developer would care to implement a way to pass a position into their engine using the iPhone's URL scheme, I would be more than happy to find a way to make my database program pass a position along to another app to play against.

Is this something in development, and if so, is it a database app and/or something that one could play against?

I hear what you're saying..  There is nothing (yet) that can do this.  In fact the only hand-held that supports variations that I know of is a Palm device (i.e. running Hiarcs 12).  I was a bit sad that the iPhone version of Hiarcs (released much more recently) lacked that feature!  Equally sadly, the Hiarcs app hasn't seen much active development since it first hit the store.

nice post, though I won't think I would buy it. I think it's hopeless trying to study chess on an iPhone since the screen is so small. However I do think it would be nice if it would be more easy to import/export PGN files. (podcast?)

I'm REALLY looking for an app that has several thousands of tactics (no only mates!) and that rates you on every theme. So that if you would fail to see a discovered attack a couple of times, your iPhone would registrate that and comment you on that. Or give you extra tactics with discovered attacks.

Already off topic but wanted to share to thought ;)