The new bitcoinj release that will be announced shortly has some initial code for BIP32. It's definitely something I want to integrate. It's difficult on mobile devices because they don't have any swapfile, so you can't just use as much memory as you want. You have to define a key window in which money can be received. Coins sent to keys that fall outside that window won't show up which is obviously very problematic. All in all, it's delicate and will require some careful experimentation and testing to make it work.
The BOP android wallet to be released in conjunction with our payment solution uses BIP32.
The mobile uses the next even index of BIP32 as change and odd as next receiver addresses. The server implements a single pass scan using a BIP32 public key, that generates an increasing look ahead window from last seen address on the block chain.
Yes it does, but we have a strategy to reset the effort. Knowing current master key birth time point limits scan as we only have to scan blocks thereafter. Now, the BOP wallet does not directly use the root BIP32 master, but a current master child of that and rolls to a new master child at user's request thereby resetting birth and scan effort. I consider making these rolls mandatory after a threshold use.
