The biggest challenge is writing scanner
software is not the GUI. It is deducing the scanner's
command set (when writing control software) and the radio's
memory image layout (when writing configuration/cloning
software).

The latter is especially challenging
because most manufacturers won't share the info
without signing restrictive nondisclosure agreements.
If you don't want to be bound by such
handcuffs, you must learn the memory image
layout through your own experimentation and by sharing info
with other developers.

It gets real tough when manufacturers intentionally
encode the image information in nonintuitive ways.
You've got to love solving puzzles :-)

There are many free tool kits available for writing GUIs,
especially if you steer clear of Microsoft proprietary
stuff. You have a lot of freedom when designing the
GUI, especially if you use open source software.

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Bob Parnass, AJ9S GNU/Linux User http://parnass.com