I was going to come on and say that be careful - you'll get a real backlash re push presents.
Personally, I like the idea but hate the name! For me, the thought that DH would have wanted to think about what would make me happy (outside of the obvious like doing his fair share of the childcare, night wakings, nappy changes etc) would have been lovely. But it totally varies by couple so I'd advise you to think carefully about what YOUR wife would like.
I used to work in the City. Push presents were quite often lots of BLING. Diamond pendant or bracelet, flashy ring etc. As DH and I share all finances, that would be less appealing to me as we would usually make a decision on jewellery together because of cost. But something sentimental would totally have worked for me - so less expensive jewellery, perhaps with an engraving I'd have liked.
A friend's husband gave her a book of IOUs for use in the first year. Obvious ones like foot rub and breakfast in bed but also a spa night away (without baby), a show etc. Which were as much about him showing her upfront that he was not going to have a problem with her going out and leaving him with the baby.
Whatever you do, avoid clothes - she'll be feeling stressy about post-maternity shape/weight. Also any gadget linked to the home or baby.
Quite honestly, to this day, if DH would just bring me home flowers occasionally, it would be huge!