If you are running an app (e.g. Pandora, Simplify Music) while your passcode-protected iPhone is locked, you can easily quit the app by tapping the Emergency Call button on the bottom left of the screen.
This saves you the trouble from having to enter in your passcode to quit an app that is running while your iPhone is locked.
Note that this hint only works with the iPhone; it does not work with the iPod touch.
It always struck me as odd that the iPhone never had a .com key for entering e-mail addresses like it does for entering URLs in Mobile Safari. But it turns out it does: hold down the period key when entering an email address in Mail or Contacts, and you'll be presented with a pop-up list of standard domain suffixes.
[robg adds: I can confirm this works on an iPhone 3G running iPhone OS 2.2.1.]
I wanted to use an external microphone with my iPhone, so I could record audio from an event. Unfortunately, there aren't any cables that give you a real microphone input jack. Fortunately, I was able to find an unexpected solution: the Mini A/V cable that came with my digital camera!
On one end, it has the three standard RCA plugs found on the front of every TV. On the other end, it's got a four-conductor mini plug that's the same as the iPhone's headphone jack. Just plug the cable into the iPhone's headphone jack, and use the RCA jacks like this:
White/Black: Audio out (L)
Yellow: Audio Out (R)
Red: Mic level input
Now, with the right adapters, you can use professional microphones with your iPhone, or feed it audio from a PC or mixing board! Just remember to add a line level attenuator before you do that, because line level will be waaaay too loud. This comes in very handy with audio recording apps.
Unfortunately, the input is only mono, but it sure beats the internal mic.
The current version of the iPod.app on the iPhone and the iPod touch has a strange bug which prevents updating Smart Playlists based on criteria which change when playing from the playlist.
That sounds a little bit complicated, but there's an often-used and simple example: a playlist based on play count (e.g. Play Count -- equals -- zero). When you play titles from the playlist on the iPhone, they should disappear automatically after playing, which currently isn't the case.
The workaround, as described in this post on Apple's Discussions site, is to create a second Smart Playlist. For the second Smart Playlist, set the criteria to simply this: Playlist -- is -- [the troublesome Smart Playlist]. When you now play titles from this new Smart Playlist, the criteria change properly, and both playlists change accordingly.
[robg adds: I can confirm that my iPhone 3G exhibits this problem -- I have a Play Once smart playlist, and the number of songs in it remains constant even after a given song plays through.]
If you get a text message when you're in an application and don't want to leave that app to respond, but you're worried that you'll forget about the text message when you're done, here's a simple solution...
When the text message arrives, push the lock button to lock the iPhone's screen. Then press it again and unlock. You'll still be in the same app, but the text message dialog will be gone. When you exit the app, you'll see the red "1" counter on your SMS icon, reminding you to respond to the text message.
If you are syncing your iPhone and want to make a phone call, you'll have to cancel the sync.
However, if you're already on the phone and want to sync and continue talking, the iPhone won't drop the call. So, syncing while talking is possible if you need to do it; just start the call before syncing.
There are lots of GPS applications for the iPhone which do live tracking of your position via GPS. Sadly, most of them don't work when the iPhone display is switched off. There are some exceptions, though. The newest release of RunKeeper Lite seems to include a workaround -- according to their blog, the iPhone display can be switched off and tracking still proceeds. Trails.app includes a nice display dimming feature, which switches the display off automatically when put into the pocket.
At least for some other applications, the following hint might be useful: If you start playing music with the iPod application, then open your GPS application and start tracking, you might be able to switch off the display with the lock button without losing tracking capability. If you turn the volume down, you won't hear the music. This may not work in all apps, so just give it a try.
The preferences for the iPod program on the iPhone/iPod touch does currently have an option to hide compilations from the Artist's view. If your artist list is also filled with these entries, and you're annoyed by that, the first thing to do is probably to tell Apple about it.
As a temporary work around, create a Smart Playlist that contains only compilation tracks -- simply set Compilation to is true in the Smart Playlist setup. Next, select all tracks in this Smart Playlist, open the Info dialog (Command-I), go to the Sorting tab, and enter a special character (e.g. . or #) into the Sort Artist field. After synching, all compilation tracks appear at the end of the artist list (of course, in both iTunes and on the iPhone/iPod touch).
I got this tip from a post from "discostevie" in this thread on the Apple Discussions site.
As you're probably aware, the iPhone is supposed to learn new words as you correct its suggestions--each time you click the 'x' box to reject a spelling suggestion, for instance, the iPhone should be noting that behavior. At some point, it will then stop suggesting an alternative when you type that word again. However, for some people (including me), it seemed this training wasn't working. I was using Notes to do my training, as it seemed like the most logical spot to do a lot of typing.
However, it turns out that that's a very bad spot from which to try to train your iPhone. Ars Technica's Erica Sadun explains why in this entry. Using a jailbroken iPhone, Erica was able to see that the customized dictionary was never updated when she typed new words in Notes. So basically, any attempt to train in Notes would be futile.
She then switched to Mobile Safari, and found that when she entered new words in the Google search box, they were immediately added to the dictionary file. In short, not every app on the iPhone seems to be capable of modifying the custom dictionary, and Notes is one such app. So if you're trying to add words to your iPhone, give the Google search box a try instead, and check out Erica's original post for more gory detail on this 'ducking iPhone' problem.