The B4x products allow one to write native apps in BASIC. With some tweaking, it appears that Android apps can be converted to iOS apps (and vice versa), allowing much of the code to be shared. The B4i and B4a products can be purchased as a bundle for under $200. That isn't the same as free, but the license to use those products never expires. Also
applications developed with B4a and B4 are royalty free. So it is just a one-time purchase. It might be worth the expense in order to have apps that run on two popular platforms.
There are also B4j and B4R products that support desktop and Arduino (respectively), and are available for free.
It might be interesting to try B4j to develop a simple interface to control a transmitter over USB, since there would be no cost involved.