When I hit the tablet side of things I did two search fields on the Android like this:
Code: [ ] Description: [ ] [x]
You could fill in one or the other and I blank the one you are not using. Works nicely and there is plenty of horizontal space in either portrait or landscape to pull that off. Codes are small so that entry field eats up less horizontal space.
On the iOS side I am using the UISearchBar and it supports only one entry field. I was going to give up on doing the dual search on the iPad but then I discovered the scopeBar and associated methods on UISearchBar. You can set various button titles and that allows the user to toggle the type of search they are doing.
It works and I have converted the code to use it but there is a bit of oddness to it. First the toggle buttons always appear below the search bar. It would be nice to move the buttons to the right of the search bar on the iPad as I only have two buttons in most cases and plenty of screen space. Might as well show more search results. This makes for some very long toggle buttons on the iPad.
Second you can toggle the search mode then tap to type the text but once you do that the toggle buttons are disabled. You have to cancel the search, change the toggle button, restart typing your search if you entered in the wrong mode. Seems this is all one control so why disable part of it?
To save space on the iPhone it would be nice if the toggle buttons only appeared after you invoked the typing of search text. Right now they waste a lot of screen space on that small screen for the ability to toggle which is probably not used very often.
Finally there is only one keyboard mode for the entire search bar. I want it to be in numeric mode if they are doing a Code search and in alpha mode if doing a Description search but I can't do that. If my search involves Code / Description instead of Last Name / First Name I start in numeric mode but they have to manually toggle back to alpha mode to type description. I covered the 95% case here but wish I could cover 100% instead.
While initially I was happy with Apple for providing a generic search control I ended up frustrated due to its lack of flexibility. On the Android I started out thinking "Where is a generic search widget?" Implementing one was easy enough but I should not have needed to do that. I ended up with an exact layout for my needs and more flexibility in the end under Android. Typical programming issue that occurs when you are developing on multiple platforms.