Bitcoin SMS Alert
Bitcoin SMS Alert is a Windows based PC application that sends SMS text alerts directly to a user's phone. The current version obtains price information using API's from either MtGox.com or BitcoinCharts.com in three different currency denominations (USD / GBP / EUR), and will alert the user if price and/or price percent changes have have exceeded a given upper or lower bound. Other features to prevent too many text alerts, and different update intervals are included as well.
Unlike some other monthly services that exist, this program costs only a one time fee of $2.99 USD payable via MtGox instant BTC checkout. Updates are provided free of charge if an e-mail address is supplied upon checkout. The author claims that custom tweaks / upgrades can be made for small donations.
Current Version: v1.1 (Made available on August 28, 2012)
More information and a video demo can be found on the website.