Most platforms and mobile devices have apps which understand the "stardict" dictionary format. As a result, you can easily add new stardict dictionaries, and search them. Here, you will find stardict files for sanskrit dictionaries (monier-williams, apte), and grammar texts.The input format is a simple subset of the itrans scheme. It is designed for ease of input on mobile devices, and should be relatively natural.
Note: this input scheme is a variation of the itrans format. It purposely omits all punctuation, which makes it easy to type on mobile devices. Since stardict applications generally accept case-insensitive input, searching becomes simple, while remaining almost lossless.
computers / laptops:
Note: the apte files were generated from the "sandic" project files. That project is available from http://sourceforge.net/projects/sandic/
These files were generated from data available from http://www.sanskrit-lexicon.uni-koeln.de/index.html
Here are some additional stardict files related to sanskrit grammer
Here are some files related to the aṣṭādhyāyī (indexed by sūtra number and sūtra text, following the hrasva mahābhāṣhya numbering)