IDA Pro is most powerful and most developed disassembler available today. It's multi-platform, multiprocessor interactive disassembler. Its main task is to convert binary executable program into assembler text. That allows you to browse through the source code of executables, reverse engineer for getting the internal source code text of the file. 

The most outstanding feature of IDA Pro is interactivity and it makes this tool unique among other disassemblers. With this program you cam browse through the input file and modify it on the fly with no waiting time and all your modifications will be displayed on the screen right away. The other unparalleled feature is FLIRT which stands for Fast Library Identification and Recognition Technology. It works like this: the program searches the input file trying to find common procedures and properly names and then assigns comments to them. In other words, it helps you saving your time and taking the routine work away.

IDA Pro unique features:

• common library functions recognition (FLIRT)
• interactivity of processes
• advanced navigation system
• built-in IDC programming language
• open module-based architecture
• possibility to work wit hall popular processors (iPhone CPUs are on the list)
• possibility to work almost with all popular file formats (full list)
• multiple local and remote debugger modules, including WinDbg and GDBServer based ones
• high level constructs such as unions, structures, variable sized structures and low level constructs such as bitfields
• stack Variables keep track of your local variables, Local Variables
• graphing: through a VCG Port. See our Graphing Tutorial
• program Navigator Toolbar
• fully dynamic global and local Labels
• interactive Register Renaming makes RISC processors easy
• auto-commenting: you can even define and use your own comments base
• versatility: loads and disassemble virtually any file. Visit our gallery for a small subset

IDA Pro can be useful by iPhone baseband reversing and you will need signature files to do that as well. The files and download links are here. The disassembler can also be ported to iPhone. It can operate with all device's apps and can perform all the analysis and actions as on desktop version.