Federal exemptions have now been granted for jailbreaking in the following circumstances:
video games - to investigate or fix security flaws.
copy-protection on DVDs - educators allowed to circumvent for noncommercial purposes
bypass security dongles when they break and cannot be replaced by the computer owner
blind people may break digital locks on e-books to access read-aloud software.
Jailbreaking has been legitimized to some degree except of course the activities cannot result in other copyright violations. Note that jailbreaking your electronic device can void your warranty and potentially "brick" (kill the device so it as useful as a brick) it. Just because jailbreaking your iPhone with iOS4 is now as simple as visiting a web page on Safari, beware of malware and being bricked (by Apple). (link)
For details see US Copyright Office "Rulemaking on Exemptions from Prohibition on Circumvention of Technological Measures that Control Access to Copyrighted Works" (link)
Jailbreaking software has existed for iPhones since their inception. No longer the domain of computer experts, all one needs to do is install the software and in a matter of minutes you gain additional capabilities. Again, the caveat is that Apple considers jailbreaking a breach of your warranty and unlikely to provide support or warranty service.
Many of the iPad Hacks originate from the hacks on the iPhone.
Many e-book readers have read aloud capabilities built into the device such as the Amazon Kindle. However, publishers have asked them to turn off that capability arguing that in essence two books have been sold for the price of one (digital ebook plus audio book).
The Kindle 2 was the first Kindle to have a read aloud capability. The Apple iPad can also read books aloud.
Here are the rules from the Copyright Office announcement with my annotations in bracketed {italics}
"Persons making noninfringing uses of the following six classes of works will not be subject to the prohibition against circumventing access controls (17 U.S.C. § 1201(a)(1)) until the conclusion of the next rulemaking.
(1) Motion pictures on DVDs that are lawfully made and acquired and that are protected by the Content Scrambling System when circumvention is accomplished solely in order to accomplish the incorporation of short portions of motion pictures into new works for the purpose of criticism or comment, and where the person engaging in circumvention believes and has reasonable grounds for believing that circumvention is necessary to fulfill the purpose of the use in the following instances:
(i) Educational uses by college and university professors and by college and university film and media studies students;
(ii) Documentary filmmaking;
(iii) Noncommercial videos.
(2) Computer programs that enable wireless telephone handsets {e.g., cell phone or mobiles} to execute software applications, where circumvention is accomplished for the sole purpose of enabling interoperability of such applications, when they have been lawfully obtained, with computer programs on the telephone handset. {aka jailbreaking}
(3) Computer programs, in the form of firmware or software, that enable used wireless telephone handsets to connect to a wireless telecommunications network, when circumvention is initiated by the owner of the copy of the computer program solely in order to connect to a wireless telecommunications network and access to the network is authorized by the operator of the network.{aka jailbreaking}
(4) Video games accessible on personal computers and protected by technological protection measures that control access to lawfully obtained works, when circumvention is accomplished solely for the purpose of good faith testing for, investigating, or correcting security flaws or vulnerabilities, if:
(i) The information derived from the security testing is used primarily to promote the security of the owner or operator of a computer, computer system, or computer network; and
(ii) The information derived from the security testing is used or maintained in a manner that does not facilitate copyright infringement or a violation of applicable law.
(5) Computer programs protected by dongles that prevent access due to malfunction or damage and which are obsolete. A dongle shall be considered obsolete if it is no longer manufactured or if a replacement or repair is no longer reasonably available in the commercial marketplace; and
(6) Literary works distributed in ebook format when all existing ebook editions of the work (including digital text editions made available by authorized entities) contain access controls that prevent the enabling either of the book’s read-aloud function or of screen readers that render the text into a specialized format." {device is an ebook reader}