I make several custom searches on Pubmed (you need to register, but it's free and has benefit of creating a collections of abstracts from Pubmed, you can easily add interesting things found by browsing the Pubmed for later reading) at set it to send me an email every day when new papers fitting the seach will appear.
But of course for this to work fine, you need to think really well how the search term would be, it's essential to use advanced search options, ude several variations of the thing you are looking for (like: (IL3) OR (IL-3) OR "interleukin 3" ) to be sure you don't miss anything.
But even then, in some cases many papers would fit the search. It would be probably possible to narrow it more, but I rather check four uselles abstracts each day than to miss something important. The side effect of this is, now I know in waht other cases my gene is also studied, it's interesting.
I don't put all topics into one search, I divided them, so from some topics I get the dayli digest which I know often doesn't have anything relevant, and others just few times a month, and then there is a high chance it is relevant. You can name the searches differently for the email, so you know the topic.
But this has no "artifical inteligence" or any "paid" inteligence that selects papers, except for your own, and doesn't contain distant fields that may interest you, but you didn't know about it yet.
But you can also put into search just complete Nature or Science to keep in touch.
Also, on G+ is quite good page, of a site Neuroscience News, that keeps me posted about new research in neuroscience, which is quite far away from my reasearch, it's a bit "easied-up" short summ-up, but links to the original articles if you want to read them.