Originally Posted by Mirch

I would respectfully correct the last example. Quran does not permit you to forgo your salat even in the middle of a war. There is a method of offering it in those circumtances. Having said that if a person fears that he will loose his job if he offer his prayer at his work and he or she is not permitted to offer his salat at work. In that case Allah has permitted us to offer our salat in whatever manner we can pray.

]فَإنْ خِفْتُمْ فَرِجَالاً أَوْ رُكْبَانًا فَإِذَا أَمِنتُمْ فَاذْكُرُواْ اللّهَ كَمَا عَلَّمَكُم مَّا لَمْ تَكُونُواْ تَعْلَمُونَ (239:2

When you are exposed to danger, pray on foot
or while riding; but when you are safe remember God in the manner He has taught you which you did not know. (2:239)

There are some hadees which validate my understanding which tell us that our holy prophet sometimes prayed when he was riding a camel. In this case since it is not possible to make ruku , sajood in its right format so even if you are praying with gestures or in your heart that is better than not praying at all.
Some muslim scholars tell us that this verse pertains to Nafil salat only not fard , but as you can see clearly Allah did not make any distinction here as to if this verse applies to fard or nafil salat.
There can be some situations in which you cannot pray in any manner like while you are operating some machinery and there is a danger that you will cut your limb if you do not pay full attention that is the only situation where I will forgo my salat and ask forgiveness of Allah.
Wallah Alim Bis Sawab . Allah knows the best.