Any stepup ratio is possible. You could try putting the requirements in to the tools on National Semiconductor's site, although I often find it comes up with 'no solution' for my applications and I have to do the design by hand.
For low input voltage, high output, try the Linear Technology LT1308, I think it is. I will check tomorrow when I am at my computer.
Possible yes, reasonable no. The switched power (and also the expectable switching losses) of a single inductor buck or
boost converter are a function of Imax * Vmax, increasing with step-up (respectively step-down) ratio. If the power is
low or efficiency isn't an issue, factors of 10 to 20, or even more may be acceptable, but a transformer gives usually
better performance.
2V to 28V is only 14x. I have done 24x with the LT1308 and more than 50x with other circuits. I cannot remember the efficiency, but with the 24x LT1308 circuit I know it was reasonable because it was a battery powered product where I had to meet a specification.