The current sending by IP is not very useful: it connects to the IP, so you'd like to use TOR for anonymity, but then it can totally be eavesdropped and man-in-the-middled.
The future plan for sending to an IP is to make it a bitcoin address plus IP, like:
1auaDZCFYqaGx4FKS5WenNfurk2SkoDu4h<someseparatorcharacter>1.2.3.4
or
1auaDZCFYqaGx4FKS5WenNfurk2SkoDu4h<someseparatorcharacter>domain.com
I need suggestions for the separator character. ":" is a candidate, but IPv6 has : in it and that might get confusing. Something that's allowed in url parameters would be nice.
I want to use SSL for the connection, using the bitcoin address' public key as the cert. You would be certain you're connected to who you thought, and safely encrypted. The bitcoin address would not be used for the transaction, only for authentication. A new generated bitcoin address would be sent through the SSL connection.
Since it's authenticated, it would then be safe to allow the IP address to be a domain name. Some care taken that if a proxy is used, it uses socks4a instead of DNS lookup.