As of version 1.5, Interstellar Force has support for iControlPad.

The iControlPad is a Bluetooth gaming controller which supports almost any smartphone, tablet or computer.  The photo to the left shows the iPhone 4/4S docked in an iControlPad

It’s compatible with a host of emulators, including NES, SNES, Megadrive/Genesis, MAME, PC-Engine, MSX, Gameboy, Amiga, C64 and more.

And with iCade mode you can play  several  App Store titles including Interstellar Force.

Features Include:

• The worlds smallest, lightest and fully functional bluetooth gaming controller
• Compatible with iPhone, iPod Touch, Samsung Galaxy S2 and many, many more
• iCade emulation for over 30 compatible App Store games (no jailbreak required!)
• Dual analogue nubs, digital D-Pad, 6 face buttons and 2 rear buttons
• Bluetooth connection with HID keyboard, joystick and gamepad modes
• Universal Metal Clamp, for attaching it securely to almost any phone
• Dual analogue on your iPhone without jailbreaking!
• Internal 1360mAh rechargable battery, with support for charging your phone via USB
• Upgradable firmware, new features can be added and restrictions bypassed
• Exclusively made in the UK and Germany

iControlPad rear view with iPhone

Here in the USA, the iControlPad is available at Think Geek

Image credit: iControlPad.com