If it is only an application, just find a mobile phone and use it. For example, an old mobile phone with a debug download cable can be used for development. If you are only working on applications, it does not seem necessary to buy a special development board, unless your application involves hardware such as various sensors.
However, if you are working on the underlying platform, there should be many platforms that can run Android, depending on the specific target positioning and hardware selection route. For example, BeagleBoard/PandaBoard are both TI platforms, especially PandaBoard is relatively high-end. If you are a product, it is estimated OMAP4’s CPU price and supply are both problems, and OMAP3 is okay. For example, the Atmel 9G45 platform can also run on Android, but the 9G45 is still the ARM9 platform, which is good at stability and is more suitable for industrial control products.