Which pays about 7mbtc for every 1btc if I am not mistaken
Actually it's 1GB for every 16 BTC and -at this thime- 1GB is worth about 0.31BTC, so it's around 0.019BTC for every BTC.
Signing this message (a GBYTE address) with a BTC address containing 100 BTC would give about 6.25GB or 1.94 BTC, so about US$5,000, not "several hundred dollars".
I really don't like the lack of information here. I don't think OP should profit from that.
A full disclosure would be appreciated and, if people want to use OP's service in order to avoid installing the wallet or to save time, then that's fine. But not just because they don't know what's happening.
So
here's the information, or
here.
If you want to save some time and continue with OP's offer then go ahead...