DM Tool Kit
RPG Cartographer
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Level 99 Games - Games, Game Utilities, Game News
Battle Map, but it's $30.
So, I've got the DM Tool Kit from lvl99 games and think it's a decent enough program. It's got some decent enough potential and while it might not be as "awesome" as running a game using a full laptop is concerned, I think it's useful enough that I don't regret the money spent on it.
Like a lot of thing in life, it's going to be rather difficult to have a "one-stop shop" solution. You're going to need to have a good idea of _what_ you're looking for and then find individual things to fill those needs as you go along.
For example, DM Toolkit combined with Good Reader (a pdf reader) is a great way to go. Look up rules or whatever using Good Reader and then switch to DM Toolkit for management of some of the game aspects. If you want to take the time, you can create some stuff to bring rules references into DM Toolkit, but it's a bit rough and requires some work.
RPG Cartographer from lvl99 games, I don't really know a whole lot about. At this point in time, it doesn't do what I want it to so it's not worth my purchasing and hoping it'll be improved to that point later.
I did spend the money on Battlegrounds and find it to be a pretty stellar app. However, as with everything, there's some work involved. You've got to create the maps, you've got to come up with the tokens/pieces, etc. Now, you can go "low tech" and go really rough, or you can try and get all fancy using maps partially created using something like Dundjini as a base and overlaying Battlemap stuff on top of it after importing the map into Battlemap. Or you can go all out and make the map using Battlemap.
$30 is quite a hefty pricetag. For me, it's worth it because it does what I want for a program like that. Line of sight, lighting, TV/Monitor out, all sorts of nifty stuff. You can always get around it though by using other programs.
For example, Sketchbook Pro. Import some sort of grided sheet as a layer, and then simply draw on top of that... you've got your own version of the classic battlemap. It's not going to be as nice/fancy as Battlemap, but it's another approach.
Yes, there's also a project going on to have RPTools work on the iPad. My understanding though is that the actual program is going to be running on a computer/laptop and then the iPad app will connect to that as a sort of client. Not saying that's a _bad_ thing, but it's going to rely on having some sort of connection, as well as another machine running.
Depending on how fast it runs, you might just be better off setting up Team Viewer and running that (or any other desktop remote app) so you can have it all on the computer and the iPad simply becomes a touch-monitor.
One thing that some gamers swear by is "TiddlyWiki". They use it to keep track of campaign notes and all sorts of other stuff. The iPad isn't able to natively run a tiddlyWiki like a computer, but there's (or course) an app that will let you do so:
TWMobile for iPad on the iTunes App Store
I haven't used it so I can't comment on it specifically, but I can say that I plan on buying it and messing around with it some. I've got a project or two that I'm messing with that relies on a tiddlywiki and I'm quite keen to see how it'll work once it move from the computer to the iPad.
In terms of "overall organisation" and management of multiple GM tasks, TiddlyWiki might be the single most useful thing for you. Being able to import that to your iPad might very well be worth the .99 US that TWMobile is charging.