As a surfer already at the beach, it's not in your best interest to tell everyone its pumping. You might call your best mate to tell him to get his arse out of bed. But everyone else you'll be gladly informing some time in the future, about the epic uncrowded session you had.
Instead, think of who benefits telling people when there is surf happening right now. The nearest food shop/cafe would do more trade when the surf is on. Local surf shops too. They might post reports.
They're are also likely to splice the report with their own advertising...
The only site that I have seen that is able to somewhat get people to provide reports is www.stokereport.com, a bay area surf/social networking site. They had to institute a word filter that masks the specific names of breaks, and they will ban you if you repeatedly violate calling out spots .
This isn't me being narrow-minded, it's simply a matter of waves being a limited resource. Sharing waves is fine for beginners surfing inside and heading directly towards shore. But when you're out back surfing green waves there's not that many waves to go around. It doesn't take many people to paddle out before your wave-count drops and you have to start competing for waves. It's just a lot less fun.
As regards knowing when the surf is good, I know by looking at weather forecast. When I first moved here I put in the time checking the forecast and checking what the actual waves are like for that swell, wind, period etc. I know what any of my regular spots will be like just by looking at the weather charts for the day. I don't need an app to tell me. Anyone who surfs a spot regularly will similarly be able to tell what it's like from checking the charts.
I think the market for this kind of app is really just beginning and occasional surfers. They will certainly be consumers for the app but they will probably not be much use in providing data for the app.
Just naming surf-spots on the internet is a sensitive subject so putting almost-live photo updates of spots will be even more so. Don't expect regular surfers to provide this information.
The only benefit I'd have for this is when the big report sites over-hype a bit of weekend swell and get it wrong... Hopefully reporting that it's worse than expected would keep folks from driving out from inland.
"This report is from 2 hrs ago, hopefully they've all gone in by now"
"I'm an agressive surfer, I'll get waves regardless of how many people are out there"
"I'll hit this at sunrise tomorrow"
I can understand the sentiment from folks who don't want to broadcast good spots, but I suspect there's a good amount of people who aren't so territorial.
When I did last surf (Steamer Lane mostly), I occasionally checked the surfline cams, but more often than not would just head down regardless.
If you ever make an iPhone version, I'll happily buy it (even if it's nowadays mostly for nostalgic reasons).
It's kinda crowd-sourcing of surfcams (coz those don't really deliver)
In general, surfers don't want to help other surfers find the best spot of the day. Once you're there it's different, and many surfers are really helpful/friendly. But hardly any will say "this spot X that you've never heard of is going to fire today", especially when they know you'll head to the big town beach break away from them ;)
I know surfers that'd give me a lot of shit if I posted video of a spot firing. I know I might do the same if I found out ;)
My suggestion would be to make this a private group thing. Create a, ahem, "circle" of surfers and share reports with them.