You may use something else in place of cash. But unless it's high-value goods or machinery, the general recommendation is that you take cash. The estimates are just too much hassle and when you get them wrong the tax office might intervene and that's something you might go to jail for since it may count as tax evasion. Now if you have an app that's worth a million bucks, go ahead...

Yes, but who evaluates how much it's worth? And why the hell should someone even have to be doing that? It's utterly useless bureaucracy. If the goal of having capital is to cover wages, say, should the company go under, then you should have that specific requirement, not some vague notion of 25K being a magical number.