I agree with you, but maybe using an optical trackpad as the previous Blackberry phones, the Samsung Omnia or the HP keyboard I linked before would work for a fraction of the cost, and much easier integration (the whole keyboard doesn't have to be reworked for that). What new Blackberry phones have is the fusion between a touchpad and a keyboard, and that must be more complex than a mere (and small) optical trackpad:





Dx was selling them for just 10€ (currently out of stock), but I'm sure those or alternative models could still be sourced somewhere. I think I have seen smaller trackpads too.

Also, since it's optical and not based on conductivity, it can be used with gloves (but I don't expect the hwkb to be very comfortable with gloves ):



Could be useful for simple (no typing) use in winter, although it isn't really a serious argument.