Although I was an early adopter (I had an original color Palm phone - the Samsung SPH-i300 for 6 years before switching to a combination of Motorola Razr for personal use and Treo 650W for work), I resisted the masochistic urge to get an iPhone, was tempted by the Palm Pre, but waited patiently for the arrival of my now-beloved HTC Incredible (aka Verizon Droid Incredible). With about 80 additional apps (and counting), I frequently review new apps and consider developing new apps. The question arises: do I develop in Java using Google's Android SDK? (My Java skills were last used around the time I got the SPH-i300: 2001). Maybe...but what if there was a way to develop mobile apps for multiple platforms, say iPhone and Android, and maybe Blackberry, Symbian, WebOS (Palm) and Windows Mobile?
Actually, there are at least 3 - and, incredibly, they're FOSS (free, open source software):
Note: a fourth commercial product, Ansca Mobile, currently in Beta for Android support and primarily supports iPhone for game development.
Read more for additional details and initial impressions of these products.
Appcelerator's Titanium Mobile (which, through it's co-founder Jeff Haynie - possibly related to my dorm-mate Kevin Haynie - has ties to the Georgia Tech Advanced Technology Development Center where I worked on my senior design project for now-defunct Hayes Microcomputer Products) supports the 2 of the 3 top smartphone platforms (Android, iPhone) and uses standard web development technologies: HTML, JavaScript, and CSS. It can also use existing Objective-C (iPhone) or Java (Android), and can be used with other Appcelerator products to develop applications for desktop platforms (Linux, OS X, and Windows). And, according the company, the product compiles native apps, which should provide better performance and a user interface that is familiar to the target platform.
The original multi-platform development toolset, PhoneGap, supports the top 3 smartphone platforms (Android, Blackberry and iPhone) and uses standard web development technologies: HTML, JavaScript, and CSS. It creates web applications that interface with the platform's APIs.
Rhomobile's uses Ruby and HTML and supports all smartphone platforms, but its GPL v3 license (not to mention my lack of Ruby experience), puts a damper on this option for those developing commercial products. But it's RhoSync and upcoming RhoHub products show a level of market savvy missing from other products.
One limitation for iPhone developers on all products: thanks to Apple's proprietary rules, you can only develop on a Mac (or Hackintosh) platform.
For more lively discussion on this subject, see this interesting article on StackOverflow.com.