Is the limit from blockchain's API that high? I thought it was something like 1 request/s.
It should be fine for what you're trying to do. Furthermore, it's hard to believe other blockchain explorers won't have any limits.
Blockchain.info website says:
Requests in 8 Hours: 1 (Soft Limit = 30000, Hard Limit = 30500)
Requests in 5 minutes: 1 (Soft Limit = 500, Hard Limit = 525)
I initially thought it says "1 request per 5 minutes" but I guess I misunderstood it... So if it gives 500 requests per 5 minutes which ought to be enough for me, but I want to check a few addresses at the same time so those limits might still become an issue if I want to update it in real-time. I'm sure blockexplorer.com also has its limits to prevent abuse but maybe they're not as strict.
But anyway I'm still left with the puzzle on how to get nothing but incoming values individually from the API. I'm taking a better look at it to see if I can figure it out, but hints would still be appreciated.