I'd personally like to very, very strongly argue in favor of this as an actual currency redesign, precisely because of the primary argument used in these conversations: that thinking this way doesn't put much money towards dead children, but makes you very miserable. The thing is that, if EVERYONE thought this way, or just everyone in a large developed country like the United States, even if they only devoted 0.1% of their income (at least 1%, probably more, sounds more reasonable), the price of a dead child would DRAMATICALLY rise. That would result in proportionately less misery brought on by thinking this way- which is EXCELLENT news for someone who already either thinks like this or feels like they ought to, like me.
With regards to 2: Something like "Child's Life", or perhaps simply "Life" or "Human life", would probably be a more useful term as currency.
I'd also like to point out that this has other major advantages besides getting people to donate more of their income, in economic and similar discussions. The main thing is for purposes like government budget: it would make it outright IMPOSSIBLE to say things like "how can you put a dollar value on human life", because you'd literally be saying "how can you put a Human Life value on human life?". You could still say "how can you say this person's life is worth less than 100 Human Lives?" or the like, but then at least you'd be making a clear and logical non-utilitarian assertion, rather than confusing people.
I do however think that Dmytry's complaint that it puts too much focus on saving raw numbers of immediate lives, and not enough on things like scientific research or the like. In fact, as with organized religion and the like, it might actually hurt publicly- or charitably-funded scientific research thanks to people saying "how can we spend X Human Lives on this?", although hopefully that would be averted for research areas where there's an obvious direct connection to future lives saved.
From Yvain's 'proposal' to measure money in dead children:
This makes sense to me, to a limited extent. You can spend money for your own benefit or to help others elsewhere, and there really are people who wouldn't have to die if you would forgo some luxuries. Making this tradeoff more explicit ("we're looking for an apartment costing no more than six dead children annually") might lead some people to greater generosity. It's a way of abstracting compassion.
Two things worry me, though. The first is that there's a big focus on spending here [2], but increasing earnings deserves more focus: getting a raise or a new job that added $10K to my salary would let me keep more children from dying than would reducing my spending on myself to zero. [3] The second is that thinking of all your purchases in terms of dead children is likely to make you miserable. Not just that, but miserable to little gain: you still probably spend almost as much money on yourself, you just feel more guilty about it. Much better, I think, is to pick a rule for how much to give and then apply it to money as it comes in. That way each purchase has no effect on the number of deaths you're averting.
(Note: I also posted this on my blog)
[1] The current number is probably closer to $2K.
[2] Maybe this is because it sounds weird to talk about salary in terms of dead children? ("I wonder what job earns me the most dead children?") Perhaps for earning the unit should be the "undead child"?
[3] In 2011 Julia and I lived on $18K for the two of us, not including taxes or health insurance.