I've posted a few times about this; I'll summarise here, as the post numbers I've cited before have changed with the new forum system. My original post, which I updated a few times, but doesn't seem updatable in the new forum system, was #160; today it shows as #161 if I seek it by content (string "Tensive adhesive conductive gel", with quotes), or #158 if I enter it into the post number box at the bottom. of the page. Link is
The Zeo clock transmitter (and presumably the mobile) works perfectly with some standard disposable ECG electrodes, designed for one use, but actually lasting at least 10 nights. There are no problems with expiry date or the time the bag is open (officially electrodes should not be used more than 30 days after the bag is opened. I am using electrodes that expired in September 2012, and have used them from a bag opened 10 months before; they worked just as well as a freshly-opened in-date pack). Electrodes can reliably be used for 10 days, longer with special care, so cost is not an issue (using 3 new electrodes every night costs a lot). To get more than a single night's use, surgical tape (Hypafix) and adhesive conductive gel (Tensive) must be used. It's a little messier than a headband, but easy enough. The details, which are critically important, are in the post I cite above.