A second head/third hand

[Rachel Adams]

Would a native speaker of English understand what is meant by a "a second head" and "third hand"?

"My friend sometimes jokes and calls his computer his second head and third hand. They have become so important that he says they have become a second head and a third hand to our lives."

 

[Tdol]

More or less, but they're not great descriptions as they come close together.

 

[Rachel Adams]

More or less, but they're not great descriptions as they come close together.

What do native speakers use instead?

 

[Yankee]

Yes, in that context.

 

[Tdol]

How about saying that the computer is an extension of himself?

 

[Tarheel]

I sort of get the "second head" thing, but "third hand" totally escapes me.

 

[Rachel Adams]

More or less, but they're not great descriptions as they come close together.

Is this part correct "they have become so important that he says they have become a second head and a third hand to our lives"?
I mean is adding "to our lives" correct?

 

[tedmc]

Is this part correct "they have become so important that he says they have become a second head and a third hand to our lives"?
I mean is adding "to our lives" correct?

It doesn't make sense. How can body parts add anything to people's lives? They probably have become so useful and indispensable that they have become part of physical selves.