CHICAGO – For eight nervous months, while her blood pressure rose and her nails thinned, Illinois hospital executive Pamela Davis wore a tiny FBI recording device under her shirt.

She recorded conversations starting in 2003 to document a shakedown scheme that involved hospitals and a state board, kicking off an investigation that eventually reached – and brought down – the state’s highest elected official.

The FBI said Davis’ help was invaluable in an investigation that eventually collected enough evidence to charge and lead to the conviction of former Gov. Rod Blagojevich, who will report to prison today for corruption.