Is it possible to use the OData SDK with Sybase Unwired Platform to develop a native Android application which connects to a non SAP EIS system, for example a WCF Data Service?
Given that OData is a standard, you would think that your assumption is sound. I can't speak for other SDKs, but I can say that the WCF Data Services client will consume many different flavors of OData very well.
In most cases our client adheres to the standard; where it doesn't it is generally due to some provider we've found that has deviated from the standard and so we will consider relaxing our client in that case. For example, we will parse "True" or "False" as valid Boolean values even though the spec says that the value must be "true" or "1" or "false" or "0".
I know a number of people writing OData clients for Android use OData4J - you should consider trying that if you run into problems with the Sybase OData SDK.