If you don’t already know about push notifications, a brief primer: they’re basically just like text messages, except they can be routed/categorized in ways that make them useful to individual applications on your phone.  Instead of getting a generic SMS text message when someone DMs you on Twitter, you can instead use push notifications to have the Twitter app on your phone realize a new DM has come in and alert you according to your personal settings.   When you “view” a push notification, you can be taken to a web page or app that’s relevant to its content.  Best part: the messages don’t count against any text messaging limit (for now).

I started using Prowl about 9 months ago.  My three main uses were:

• Notifying me when certain types of e-mail messages are received (using a combination of Procmail and prowl.pl)
• Notifying me when I’m addressed or mentioned in certain IRC channels (using the prowlnotify.pl script with irssi)
• Notifying me when I’m mentioned on Twitter (using Preyfetcher)

Prowl worked great, and I was very happy with it for these uses.

Recently, I had an itch to scratch with push notifications, and when I looked for someone else who might have already scratched that itch, I noticed that Prowl was last updated in August 2009.  Some of the things I wanted to be able to do with Prowl would need to be custom built.

But wait! There was this hot new app/service called Notifo that seemed to have a much more active user community developing cool new uses for its platform (including a solution for the itch I wanted to scratch).  With plans to launch an Android and Blackberry app soon, releasing their iPhone app (last updated in September 2010) for free, and a well thought out API infrastructure, Notifo is clearly positioning themselves to be THE realtime mobile notifications service.

And it turned out to be a drop-in replacement for Prowl.  The most recent version of the Twitter app for iPhone now includes push notifications, so I’m down to two uses for Notifo:

• Notifying me when certain types of e-mail messages are received (using a combination of Procmail and a custom notifo.pl script using WWW::Notifo)
• Notifying me when I’m addressed or mentioned in certain IRC channels (using the notifonotify script with irssi)

I’m also playing with some other uses:

• Notifications when new items appear in certain RSS feeds
• Notifications from our Nagios-based server monitoring infrastructure
• Notifications when certain activities happen on blogs that I maintain
• Re-routing my real SMS notifications through Notifo so I don’t need to pay for an SMS messaging add-on to my phone plan

Prowl remains a usable and time-tested solution, but the app isn’t free and the community around it seems stagnant.  Notifo is newer and shinier and will probably have some growing pains, but they’re doing it right as far as I can tell, their app is free, and their interface is more flexible.

If you’ve tried one or both out, what do you think?

Regardless of what you think of it, the “realtime web” is here, and I’m enjoying playing around with what it has to offer.  (Beyond the scope of this blog post is addressing the fundamental question about whether or not it’s a good thing to be increasing the number of disruptive, “look at me now” events I have in my daily life, but your smug comments on this matter are still welcome.)

I’m using a 1.5GHz Powerbook G4, which uses the PowerPC (PPC) architecture. I downloaded version 2.2 of the iPhoneOS SDK, build 9m2621-final.

After the regular installation of the iPhoneOS SDK (which is really just the regular Xcode install with some additional packages thrown in) was complete, the Xcode new project menu was notably missing the option to choose the iPhone platform. On the advice of this 3by9 article, I took these steps:

1. Mount the SDK installer disk image
2. Open the packages folder
3. One at a time, install all of the .pkg files that begin with “iPhone”, using the default install destination
4. When done, you’ll have a “Platforms” directory in the root level of your Mac’s hard drive. Move the contents of that directory into the /Developer/Platforms/ directory. If you’re like me, when you’re done, you’ll have three directories in /Developer/Platforms: “iPhoneOS.platform”, “iPhoneSimulator.platform” and “MacOSX.platform”.

Once that step is done, you’ll be able to launch Xcode and create new projects that use the iPhoneOS platform and application types. But, you still won’t be able to build or run those applications, because Apple has hardcoded the “i386″ (Intel) architecture as the only valid one to compile for. Thanks to a variety of comments on the above 3by9 post and comments 23-25 on this TUAW article, here are the remaining steps to address that:

• Close Xcode and edit this file (perhaps after making a backup): /Developer/Platforms/iPhoneSimulator.platform/Developer/Library/Xcode/Specifications/iPhone Simulator Architectures.xcspec
• Change line 12 to read Name = "Standard (iPhone Simulator: i386 ppc)";
• Change line 16 to read RealArchitectures = ( i386, ppc );
• Add this chunk before the last closing parentheses:

       // PowerPC
       {
            Type = Architecture;
            Identifier = ppc;
            Name = "PowerPC";
            Description = "32-bit PowerPC";
            PerArchBuildSettingName = "PowerPC";
            ByteOrder = big;
            ListInEnum = NO;
            SortNumber = 106;
       },

• Save the file and close it. Now relaunch Xcode.
• With Xcode open and your project loaded, right click on the project name under the “Groups & Files”, and select “Get Info”
• Under the “Build” tab and in the “Architectures” menu, change these options:
  Set Architectures to “Native Architecture of Build Machine”
  Set Base SDK to “Simulator – iPhoneOS 2.2″
  Leave Build Active Architecture Only checked
  Edit Valid Architectures to be not only include armv6, but also “ppc” and “i386″.
  (I think some of these may be redundant, but it’s the combination that’s working for me.)

When you next build your project, you shouldn’t get any errors about VALID_ARCHS.

I hope that’s helpful. Since this is only one particular combination of build hardware/architecture and SDK software version, I’m sure there are other combinations out there where the above may not work, your mileage may vary.

Now, back to working on building an actual application…