Is there any online tools which lets me submit code in Obj-C and which compiles and displays the app on a simulator?
Please do share if you have any other suggestions on the easiest way to get started.
Thus, if you want to do Objective-C development, your best bet is to get your hands on a Mac. Barring that, you could rig up Hackintosh, or Hackintosh VM in VMWare/Virtualbox.
If you are willing to consider some zanier options, there's a open source project that's attempting to create a portable iPhone toolchain: http://code.google.com/p/iphone-dev/.
If you're willing to forgo Objective-C, and try cross-compiled development, there's stuff like PhoneGap, xmlvm, etc.
It might make more sense to buy your own Mac, after all. I initially assumed this service rented Mac Minis.
"We are a mac mini colocation service. In other words, we place your Mac mini in a high-end data center where you can use it as a server. We provide you with a menu of services including redundant very high speed internet connections, remote control electrical power, a highly secure location to house your Mac mini, and remote human hands."