One of these days Chad or one of the other Indy members is going to see me posting about Synapse and chew me one, but until then, If your looking cross platform Synapse is the best solution. Indy is the best solution when it comes to Delphi on Windows.

The PHP/MySQL requirements are just what I'm using for my updater, there are of course, other ways of doing things. But I needed a way to update any product/project and wanted a basic launcher that I could just place in with the app and then forget.

Currently the parts I still need to complete are:
1) Compression - I'm using raw blocking right now, bloated but works
2) Comprehensive vs Patch downloads (IE do you bring down v1, v1.1, v1.2, and v2 or just v2)
3) Making it look better

Give me a few days and I'll see if I can't get something up so you can see it.