We do not have a sample that shows how to create a custom index. The index is based on pipes, so you can check this post
You should create a custom pipe ( we will have an example with the Q1 release). You need to inherit from SitefinityContentPipe and override ReadInboundData where you can get all items with a certain parent or get them from specific database tables ( ex. hotels, restaurants etc.)
You can also check this article
which might be very useful.
All the best,
the Telerik team