You wouldn't need a full bitcoind, only to be able to do the bootstrapping of bitcoind, find a few valid nodes and send the transaction there. I guess in most cases 0 confirmations would be enough anyways... I don't know if an invalid transaction fails silently though or if the other nodes would complain if you got a fake transaction and relayed them there.
Also a possibility: Let the admin input a list of n adresses that are used for single transactions + a warning when the address pool is starting to run low. Check via blockexplorer or other services for transactions in the network or fulfilled payments.
The best and probably easiest solution would still be the LAN bitcoind I guess though. Please make it send it's traffic as fast as possible (so someone can get the whole block chain quickly if necessary).
+1 BTC from me if the solution: Works on Open WRT and DD WRT, is able to traffic shape the paying users (e.g. at least 50 kB/s per user, up to 500 kB/s for all users) and is Open Source, hosted on GitHub.
Hi, for sending you are right, in theory you dont need to allow a complete tunnelling of the bitcoin protocol. however, what I meant with running bitcoind on the hotspot device was that the owner needs to confirm the incoming transaction. As I also stated, this could be done with some other pc/vps that can be queried via RPC.
As for accepting 0/unconf transactions with this, as long as the tx is valid(it wont show up in the receivers client if it is invalid), I would consider the risk minimal - at least lower than the risk of people performing a chargeback(friendly fraud) when paying with their credit card or gaypal account.
However, long story short, I developed a similar solution about a year ago, on a D-Link DWL 622AP using openwrt. The DWL is a very small device with 2 megs of Flash, and 8 megs of RAM, so my solution should work on any openwrt device, since the 622AP is pretty much as low as it gets when speaking of system resources. I remember I solved the captive portal task back then by adding a firewall rule for new connected clients that redirected all traffic to the router itself, and remembered clients by mac and user/pass combo(having the mac enabled for as long as the wifi connection persists + 2 hours, after that asking for user and pass again). So what needs to be done is adding an little proxy that will connect bitcoind on the client machines to our payment gateway bitcoin, a teensy piece of code to verify incoming transactions, and nicer pages for the frontend(webdesign isnt really my thing). If need is there, an admin panel would need to be written too.
If there is still interest, and the bounties are still up, I might consider reopening this project for BTC.
