You can control VoiceOver on iPhone using an Apple Wireless Keyboard. See Using an Apple Wireless Keyboard.
You can use VoiceOver keyboard commands to navigate the screen, select items, read screen contents, adjust the rotor, and perform other VoiceOver actions. All the keyboard commands (except one) include Control-Option, abbreviated in the table below as “VO.”
VoiceOver Help speaks keys or keyboard commands as you type them. You can use VoiceOver Help to learn the keyboard layout and the actions associated with key combinations.
VoiceOver keyboard commands
VO = Control-Option
Read all, starting from the current position
VO–A
Read from the top
VO–B
Move to the status bar
VO–M
Press the Home button
VO–H
Select the next or previous item
VO–Right Arrow or VO–Left Arrow
Tap an item
VO–Space bar
Double-tap with two fingers
VO–”-”
Choose the next or previous rotor item
VO–Up Arrow or VO–Down Arrow
Choose the next or previous speech rotor item
VO–Command–Left Arrow or VO–Command–Right Arrow
Adjust speech rotor item
VO–Command–Up Arrow or VO–Command–Down Arrow
Mute or unmute VoiceOver
VO–S
Turn the screen curtain on or off
VO–Shift-S
Turn on VoiceOver help
VO–K
Return to the previous screen, or turn off VoiceOver help
Escape
Quick Nav
Turn on Quick Nav to control VoiceOver using the arrow keys. Quick Nav is off by default.
Turn Quick Nav on or off
Left Arrow–Right Arrow
Select the next or previous item
Right Arrow or Left Arrow
Select the next or previous item specified by the rotor setting
Up Arrow or Down Arrow
Select the first or last item
Control–Up Arrow or Control–Down Arrow
“Tap” an item
Up Arrow–Down Arrow
Scroll up, down, left, or right
Option–Up Arrow, Option–Down Arrow, Option–Left Arrow, or Option–Right Arrow
Change the rotor
Up Arrow–Left Arrow or Up Arrow–Right Arrow
You can also use the number keys on an Apple Wireless Keyboard to dial a phone number in Phone or enter numbers in Calculator.
Single-letter Quick Nav for the web
When you view a web page with Quick Nav enabled, you can use the following keys on the keyboard to navigate the page quickly. Typing the key moves to the next item of the indicated type. Hold the Shift key as you type the letter to move to the previous item.
H
Heading
L
Link
R
Text field
B
Button
C
Form control
I
Image
T
Table
S
Static text
W
ARIA landmark
X
List
M
Element of the same type
1
Level 1 heading
2
Level 2 heading
3
Level 3 heading
4
Level 4 heading
5
Level 5 heading
6
Level 6 heading
Reference http://help.apple.com/iphone/5/voiceover/en/iph6c494dc6.html