Change iPhone pin remotely
Source:

No, you can't unlock the iPhone remotely.  You can use VoiceOver to select the numbers on the screen. 


Hold down the Home button to activate Siri. Say “Turn on VoiceOver”.
Press the Home button twice to bring up the passcode screen.
Use the portion of your screen that responds to touch to swipe left and right, which will move your VoiceOver cursor to different passcode number buttons. VoiceOver will also say the button being selected, which is helpful if you can't see the screen.
When the cursor is on the passcode number you need, double tap the screen to “tap” the selected passcode number.
After the iPhone unlocks, you may need VoiceOver one last time to tap “Trust” in the dialog that comes up when you plug in your iPhone to your computer.
Copy your photos and/or make your backup in iTunes.


To turn off VoiceOver, you can say “Turn off VoiceOver” to Siri, or go into Settings -&gt; General -&gt; Accessibility to turn it off manually.