Amazon and Kobo have both launched e-reading apps for the new Blackberry tablet, with the former also planning an app store for Android phones.

Amazon, which already has a Kindle app for BlackBerry, revealed a free app for the PlayBook, which will incorporate the retailer's WhisperSync technology, allowing readers to switch between devices.

The retailer is also rumoured to be launching an app store for Android. TechCrunch reports that the store will be US-only, and that apps will have to be enabled by Amazon DRM. The apps can also be shown on Amazon.com. The blog also surmises that apps cannot be sold cheaper at other app stores.

The Kobo app incorporates Blackberry Messenger (BBM), enabling readers to buy and recommend e-books, read with a friend or group, discuss a book in real time, and exchange passages of text. The app will be available from early 2011, reports The Good E-Reader blog.

The BlackBerry Playbook, which was launched by Research in Motion (RIM) in the US yesterday (27th September) has a seven-inch screen with touchscreen and wifi, with 3G and 4G capabilities on the cards.

The PlayBook will be officially launched in December 2010. A video of the device can be previewed here.