Welcome to the forums!
OK - interesting question and a new one for me. Having a phone with an HDMI port gives me a leg up on having checked into a bit of this.
First - going from digital to RCA (composite (1-yellow)) isn't cheap - I was able to track down one or two boxes, one on Amazon that as I recall went for +200 bucks. And that was with HDMI in.
What you're asking (and very intriguing, by the way) would have that same thing adding a wifi radio, and then the DLNA software. Just for that - nope, I'm not sure we'd find one of those.
OK, how about same thing, with HDMI out saving that digital-to-analog cost? Mmmk - but we never did account for network management to get the signal from the phone to the box - and the hotel's wifi isn't really going to cut it for that (per most hotels I've been in). And to have an on-board wireless manager in addition to DLNA... I can't imagine anyone making one of those.
And if they did, I'd imagine they'd have to stick the price up to pay for engineering.
So, I looked at the new Roku boxes because I'd heard they were getting DLNA support -
Roku Player Products | Roku HD Player, Roku XD Player and Roku XDS Player
But then found that was just a bad report, per their statements -
Roku Forums • View topic - DLNA
Still, you'd think there'd be something, so looking up UPnP (the transport protocol for DLNA) gives this - and it's bupkiss, nada -
List of UPnP AV media servers and clients - Wikipedia, the free encyclopedia
Defeating the whole purpose of what you want to do is the one workaround left I can think of:
A cheap laptop or netbook that hardwires to the hotel TV (The old Sony VAIO laptops, while bricks, were great for that) and can act as a private wireless with a DLNA client.
Sorry I couldn't give a better answer. Maybe somebuddy can find something I've overlooked.
Great question though!