I'd like to do some development of smart phone apps and my native programming language is java.
The first application I'd like to write will need to be able to (attempt to) connect to a network (LAN or WiFi) automatically in the background (on a schedule).
would an android phone be the best path or are there competitive purer java options?
I would definitely go with Android, extensive SDK, community, and increasing popularity. I think the What is Android answer on the developer web site says it all.
"Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language."
I think Android is the best start path today.
The main options would probably be BlackBerry, J2ME for Nokia ect, or Android. I personally would recommend Android. BlackBerry is overall a little more work than Android and the pure J2ME option is incredibly underpowered in comparison to either.
Blackberries use java applications, so that wouldn't be a bad choice.