Bitcoin core supports pruning. You can set it using the -prune=<size> where <size> is the size of the blockchain you want to store. The minimum you can do is 550 Mb. Unfortunately you can't use the wallet yet but that will be fixed in 0.12
Ok that's good news. What do you mean by not being able to use the wallet? I would need to sign transactions and listen for new incoming transactions, that's all what I need. The latter requires a wallet where to keep the private keys for signing.
edit:
But I could do my thing without wallet functions, all I need is my own (possibly C++) function for signing a raw transaction with the private key I'd provide. I need the pruned mode to allow me to construct raw transactions based on specific outputs, sign them and broadcast them. Is it possible?
Wallet functionality in a pruned node was disabled because it was still untested when 0.11.0 was released. It will be enabled in 0.12.
You should still be able to broadcast transactions using a pruned node, but I don't know about getting outputs since there is no wallet and txindex is disabled with pruning.
However you can just build the master branch from github for now and get the wallet functionality and then upgrade to 0.12 whenever they release it. It should be coming out in a few weeks.