Yes, you can be fired for wearing an ankle monitor--or, for that matter, for wearing an earring the employer does not like. Employment is employment at will; that means that an employer may be terminated for any reason whatsoever which is not specifically prohibited by law (for example, you cannot be terminated because of your race or religion). However, there is no protection against being terminated for being accused of a crime, under investigation, having been convicted, or for wearing an ankle monitor for any other reason; therefore, you may be terminated for this reason.