The problem with not being able to see the Slingbox Mobile for Andriod are filters within Google's Marketplace. If you're using an unsanction operating system, or are from one of the countries that do not currently support paid application then you won't be able to see it within the marketplace. This is because the Slingbox Mobile is a paid, copy-protected application.
Available per country (http://www.google.com/support/androidmarket/bin/answer.py?hl=en&answer=143779)
Unavailable per country (http://www.google.com/support/androidmarket/bin/answer.py?hl=en&answer=138294)
Work around for Froyo Users (http://www.androidcentral.com/how-get-your-paid-apps-back-froyo)
Work around for non-rooted phone (http://www.google.com/support/forum/p/android/thread?tid=441baa3452369f21&hl=en)
Work around for rooted phoes (http://www.google.com/support/forum/p/android/thread?tid=2a55855a017b346c&hl=en)
The issue is with the fingerprint filters for your device on Google Marketplace. New firmware build loses full market access. More than once, when a operator/manufacturer makes a new build, the market app falls apart. The server doesn't recognise the market client. It's a known issue when trying to purchase a copy protected app from the Google Marketplace.
You may consider trying to get support through Goolge, to find out why its specifically happening in your case. Here's a thread with someone in a similar situation. (http://www.google.com/support/forum/p/Android+Market/thread?tid=7a1e3b1335535e85&hl=en)