There's at least one company in the market in Australia with a metal hydride absorber system[1], and it's still nowhere near cost effective for household usage (or really any usage IMO: I can't figure out where this would fit where batteries or something much larger like Vanadium or Iron-flow would not).
CHP is also, IMO, cheating since the retrofits to take advantage of the waste heat aren't simple or non-invasive - i.e. theoretically CHP could power hot water and air conditioning for me via heat pumps, but in practice doing any of that residentially is prohibitively expensive.