selecting a contact from the phones contact book
by that you mean you're using:
Intent intent = new Intent(Intent.ACTION_PICK, Contacts.CONTENT_URI);
startActivityForResult(intent, PICK_CONTACT)
to have the user pick a contact from the device's contacts app?
If so, you can slightly change the picker code to become an email-picker instead:
Intent intent = new Intent(Intent.ACTION_PICK, Email.CONTENT_URI);
startActivityForResult(intent, PICK_EMAIL);
Then in your onActivityResult
:
Uri emailUri = data.getData();
Cursor cursor = getContentResolver().query(emailUri, null, null, null, null);
String email = cursor.getString(cursor.getColumnIndex(Email.DATA)); // get the email itself
DatabaseUtils.dumpCursor(cursor); // dump the cursor so you can see the fields and data you can access
cursor.close();