This already exists a basic xpath validator in the Appium.app Inspector. Click Locator > enter your xpath > click Search > it highlights the element if found otherwise it throws an error in a popup
It works fine for finding a single, specific element such as:
//UIATableView[1]/UIATableCell[1]/UIAStaticText[1]
or
//UIATableView[1]/UIATableCell[1]/UIAStaticText[@name="Some Text"]