Vomiting a mouthful, inside or outside the prayer, would invalidate one’s ablution. Vomiting less than this amount would not invalidate one’s ablution nor prayer. [Shurunbulali, Maraqi al-Falah; `Ala al-Din `Abidin, al-Hadiyya al-`Ala’iyya]
However, excessive movement would break one’s prayer. The consideration in this regard would be whether an onlooker would consider one to be in prayer or not. Though, if unwell, one may have an excuse to break the prayer anyway.